The live video footage taken in the maternity ward by the father of the newborn child is deeply shocking. It shows his wife lying peacefully, but exhausted, on the bed after her caesarean, their baby still covered in vernix cradled in her arms. Suddenly, a policeman, in uniform, accompanied by a social worker, burst through the door. The next scene is the most heart-wrenching: the baby is gone and the mother lies slumped and defeated on the maternity ward floor.

Child welfare campaigner Penny Mellor pushes the pause button on her remote control. She has seen the disturbing images of this mother, who subsequently came to her for help, many times. But they tear her apart each time. 'Why did they have to take her baby in that barbaric way?' she asks, her face creased in anguish and anger. 'Why did they have to take the baby away at all?'

According to Penny, at least six British mothers of whom she knows personally - including Karen Haynes, whose dramatic story we featured last week - have had their newborn babies snatched from them at childbirth in this inhumane manner. A further six mothers, including Sally Clark who was wrongfully jailed for smothering her sons Harry and Christopher, have lost their liberty and been sent to prison for infanticide.

And she knows of more than 100 mothers who, in the past six years, have had their older children taken from them by family courts and put into care. All of this has happened, she says scathingly, because of incorrect or insufficiently proven allegations of Munchausen Syndrome by Proxy (MSbP). Unlike Munchausen Syndrome, a rare malady where a depressed mother is said to harm herself as a perverse cry for help, in MSbP a mother is said to cause harm, not to herself, but to her children.

Almost all of these 'tragic' child removals have been sanctioned on the say-so of experts, the main one being Sir Roy Meadow, the inventor of MSbP back in 1977, and whose evidence and use of statistics was revealed after Sally Clark successfully appealed against her conviction in the High Court.

Until the release of Sally Clark last month, Penny was a feisty voice in the wilderness coming to the aid of terrified mothers gagged by the family courts. She is currently helping 50 such mothers fight social services' departments up and down the country, which, she says are armed with nothing more than an opinion by Sir Roy and are threatening to take away their children.

These 50 mothers do not have a history of child abuse; their children have neither physical scars nor burns or blemishes. Rather, they are ordinary mothers from Wimbledon or Basingstoke or Tower Hamlets - middle class and working class - who keep on pestering their doctors for answers to their children's undiagnosed illness and who, one day, out of the blue, suddenly find themselves stigmatised with the poisonous allegation of MSbP.

But now Penny hopes the tide may be turning. John Batt, Sally Clark's solicitor, says that his client's important case cannot be seen in isolation, and that it raises the issue of other potential miscarriages of justice. Powerful people are beginning to line up alongside Penny to question just why many of these mothers - who continue to protest their innocence - have lost their children.

Earlier this month, Lord Howe, shadow spokesperson for Health in the House of Lords, delivered a scathing attack on Sir Roy and his theory. He called MSbP 'one of the most pernicious and ill-founded theories to have gained currency in childcare and social services over the past 10 to 15 years'.

'It is a theory without science,' Lord Howe said, articulating what Penny has long maintained. 'There is no body of peer-reviewed research to underpin MSbP. It rests instead on the assertions of its inventor Sir Roy Meadow and on a handful of case histories. When challenged to produce his research papers to justify his original findings, the inventor of MSbP stated, if you please, that he had destroyed them.'

Lord Howe's concern is that MSbP has so deeply insinuated itself into the language and thinking of social services that it has become an all-purpose label for problem parents and children. 'A loving but apparently fussy mother who, on behalf of her sick child, badgers a GP to take her concerns seriously, can suddenly find herself accused of abuse. Once she has a label of MSbP pinned on her, it is very difficult to remove it.'

Yesterday, speaking to the Evening Standard, John Batt paid tribute to the unique role played by Penny in helping him fight the Sally Clark case, and put her contribution into a broader context.

'Experts tell me there is no doubt MSbP exists, but in tiny numbers compared to the numbers who are actually pursued,' he said. 'A mother accused by social services has no organisation to turn to. One person who, for no material gain and for nothing other than the cause of humanity, has come to the aid of such people is Penny Mellor. She is an extraordinary human being who has helped unstintingly and often with great personal risk to herself.'

Penny Mellor has spent GBP 50,000 of her own money, has worked tirelessly, sometimes going 24 hours without a break, and even paid with her liberty, enduring eight months in prison last year for assisting one mother. But who is she?

You only have to meet Penny Mellor, 41, mother of eight, to see that she defies typecasting.

Her partner is the managing director of a food retailing company and earns more than GBP 100,000 a year. At her GBP 250,000 detached house in the West Midlands, from where she runs her national help network, there are leather sofas and original art on the walls. Her friends have dubbed her 'the campaigner in the ball gown'. And there has been more than one child-protection officer who has done a double-take at the sight of Penny roaring up, armed with files of medical reports, in her turbo-charged Nissan RS-2000 sports car.

Until six years ago, Penny was a relatively ordinary housewife with her hands full. Her seven children (she's subsequently had one more) - then aged 18, 15, nine, six (twins), three and one - took up almost all her time. She did, however, do some voluntary work as a victim-support counsellor for a Domestic Violence Forum, and she was introduced to a mother who was about to have her 11-year-old child taken away from her on the grounds of Munchausen Syndrome by Proxy.

'I had never heard of MSbP,' says Penny. 'The child had unexplained upper abdominal pain and had been referred from one hospital to another. The doctors believed the mother was fabricating the child's illness, causing her to have unnecessary medical treatment, and social workers were about to remove the child on grounds of MSbP. But the school teacher of the child, who had introduced me to the mother in the first place, saw a warm, loving relationship and was convinced the doctors had it wrong.' Penny decided to do some investigating. She took copies of the child's medical notes and went to toxicologists and pharmacologists for a second opinion.

'They came back with reports that the drugs the child had been given by the doctors were the probable cause of her pain. Slowly, I was uncovering evidence that the mother was in all likelihood not guilty but nobody in authority wanted to look at it.'

Subsequently, the traumatic removal of the screaming child from the mother's care - by police at gunpoint, in this case - deeply affected Penny. 'I began to ask myself some hard questions: How can this be happening in modern day Britain?

'How can a child be removed from a mother on such flimsy unscientific evidence? Why is it all done in secret? If she is being accused of potentially killing or harming her child, why is she not taken to criminal court where there can be an open and proper trial? And why is it that all this is happening on the say-so of just one person?'

Disturbingly, Penny recalls: 'The police and the social workers would say to me, 'We don't understand anything medical, so we have to go with what the doctors tell us.' Later I saw this extended to the judges too.

'The same expert paediatricians were called time and again. Often Meadow, of course. And even when other doctors gave contrary evidence, it was always his opinion that the judges 'preferred'.

'To me, the absolute authority given to these few doctors, who were inclined to find in favour of their own syndrome, was a recipe for systematic miscarriages of justice on a grand scale.'

Sir Roy Meadow declined to comment for this article.

Penny decided to thoroughly research MSbP and the way it was being used to separate seemingly caring mothers from their inexplicably ill children, or from their newborn children following an unexplained sudden death.

Soon, dozens of other vulnerable mothers were calling her after hearing about her through word of mouth. She acknowledges some of these mothers might be guilty but she adopts the age-old English law dictum that says she would rather 'one guilty person goes free than 10 innocent people are convicted'.

Penny proved herself a tireless voice for voiceless mothers. When John Batt was appointed to the Sally Clark case three years ago the person he turned to for information was Penny. Her children have become used to her walking round pushing a hoover with one foot, telephone in one hand, 'call-waiting' sign beeping, and a second telephone ringing in the other.

You become so immersed at the injustice,' she says. 'You get this awful feeling that no one is listening and that, unless you are involved 24 hours, you are not doing enough.' Penny has travelled thousands of miles at her own expense to help mothers up and down the country. She has rooms full of files relating to the more than 150 cases she has worked on.

'The most devastating thing is when these mothers fall through my front door sobbing after losing their children in a secret family court hearing,' she says.

Once, she was accused of going too far. One family hatched a plot to prevent social workers from taking away the child on grounds of MSbP, and Penny was accused of masterminding the plan, a charge she has always denied. Despite never having a previous conviction, Penny lost the case and was sent to prison for two years.

She was released after eight months, getting out last November. Prison was rough, she says. Her baby had to be looked after by her in-laws and an au-pair, and she had to endure being banged up with - and physically beaten up by - inmates in Low Newton, County Durham, and later Foston Hall, Derbyshire, where she broke bread with Britain's most notorious female criminals.

Until the Sally Clark case, it had been one defeat after another. Time and again Penny had to try and comfort an inconsolable mother, like the one in the video footage. That mother physically fought the police to keep her baby with her last ounce of energy but had her four older children taken from her as well - all because of an allegation of MSbP.

But the Sally Clark case, Penny believes, will mark a watershed. 'I was watching it live and I just burst into tears,' she says. 'I saw Sally's haunted look and I cried because I understood that, although she had won, everything that she had lost was there in that instant too.

'But I also cried out of joy, because I saw it as the beginning of the end. That finally people are going to listen. That finally people will demand a public inquiry that will shake up the whole judicial system and reveal the whole MSbP thing for the sham that it is