Our investigation has uncovered a systematic failure on the part of the health authorities, social services and scientific advisers to question the validity of Professor Sir Roy Meadow's theory, which claims that some parents harm their children to draw attention to themselves.

The theory has been at the centre of huge controversy after hundreds of children were taken into care over fears that their parents were capable of harming them. It was also at the heart of the debate over cot deaths but has recently been discredited after a series of high-profile court cases, which drew on Meadow's theory, were overturned.

Critics of MSBP acknowledge parents harm their children. But, as leading sceptic Lord Clement-Jones, puts it, there is a need to ask 'whether MSBP really is a scientifically or medically established condition ... MSBP by its very nature can become a self-fulfilling prophesy'.

Anti-MSBP campaigners claim thousands of parents may have been wrongly separated from their children as a result of the theory, which has been described in parliament as creating 'the equivalent of the stigma of witchcraft in the Middle Ages'.

An Observer investigation has uncovered a catalogue of errors surrounding MSBP including:

· The failure by both Tony Blair and Jack Straw to investigate the claims of a leading child psychologist and former government adviser who wrote to them warning that she was aware of several cases in which parents had been wrongly separated from their children because of MSBP.

· The failure of a government inquiry into fabricated child illnesses to interview sceptics of Meadow's theory. The inquiry published a guide to MSBP for local health authorities that has subsequently been described as 'deeply flawed'.

· The publication of a report into fabricated child illnesses by the Royal College of Paediatrics and Child Health (RCPCH) which failed to address scientific concerns over MSBP.

· The ongoing failure of the General Medical Council to conclude its investigation into another leading proponent of MSBP, Professor David Southall. In January 2002 the GMC announced it would hold a hearing into allegations that Southall made a series of false accusations of child abuse against parents. A spokeswoman for the GMC said: 'The investigation into Professor Southall is ongoing.'

The revelations come as the fallout from the Meadow affair is set to go global. Thousands of families around the world who have had their children taken into care are to demand their cases be re-examined.

The demands follow last week's revelation that the Attorney General, Lord Goldsmith, is to undertake an urgent review of more than 250 criminal cases where a parent had killed a child and in which MSBP was cited.

The move was a response to the overturning of three cases where the mother was wrongly accused of killing her children and in which Meadow's work was used. But the scope of Meadow's theory of MSBP, which he first advanced in 1977, extends much further than criminal murder trials involving infanticide.

The Government is preparing to ask local authorities to comb their records to highlight all civil family law cases which have involved MSBP.

It is thought that the number of parents who have had their children taken into care after the civil courts ruled that 'on balance' they had harmed their children, or were capable of harming them, will run to 5,000 in the UK alone.

Because the cases were heard in a civil rather than a criminal court, the judge did not have to be convinced that there was evidence of harm 'beyond reasonable doubt' and could instead rely on the scientific claims made by paediatricians. This has prompted unease among politicians.

The Countess of Mar declared in the House of Lords last month: 'There are many thousands of women who have been accused of, or labelled as having Munchausen Syndrome By Proxy, without clinical or legal assessment. They have no recourse to the courts and, each time they protest, they are told that they are in denial and that it is a sign of having Munchausen Syndrome By Proxy.'

Mar concluded: 'This is an equivalent of the stigma of witchcraft in the Middle Ages; there is no trial, and one is guilty until one can prove that one is not guilty, and one has no way in which to prove that one is not guilty.'

Concerns over the validity of MSBP were raised in 1995 in the scientific journal Archives of Disease in Childhood. 'Munchausen Syndrome By Proxy is a term I suggest we use with caution ... It is important not to harm the child by falsely accusing his mother of MSBP, thereby breaking up the family,' warned one academic, Dr Colin Morley. In the same journal, even Meadow concedes that the theory has 'led to confusion for the medical, social work and legal professions'.

Lisa Blakemore-Brown, a child psychologist and expert on autism and Asperger's Syndrome, who, as chairwoman of an organisation called Promoting Parenting Skills acted as an adviser to the Home Office, wrote to then shadow secretary Jack Straw in 1996 warning that MSBP had resulted in a mother being wrongly separated from her children.

Between 1996 and 2002 Blakemore-Brown also raised her concerns in a series of letters to, among others, Tony Blair, health secretaries Frank Dobson, Alun Milburn and Health Minister Jacqui Smith. In each case she received a reply observing only that her concern had 'been noted'. She also wrote to the Psychologist magazine, warning: 'I cannot establish a robust scientific base and am aware of a number of cases in which mothers have had children removed on the basis of this diagnosis to discover later that their children had real illnesses or disorders which were missed when the notion of MSBP loomed large.'

A spokesman for the Department of Health said MSBP was a 'matter for the Department for Skills and Education'. The DfSE declined to give a response other than to state: 'We will consider the steps now announced by the Attorney General before making further comment.'

But critics of MSBP are concerned that the Government's record suggests little action will be taken. The Observer has established that a government inquiry into MSBP in 2001 failed to interview experts who had expressed scepticism about the syndrome, or examine their research which cast serious doubts on whether it held up as a scientific theory.

The committee chairing the inquiry subsequently published a report into fabricated child illnesses which Earl Howe describes as 'deeply flawed - principally because it fails almost wholly to acknowledge that the topic is highly controversial and that erroneous diagnosis is a real risk.'

The Observer has been in contact with anti-MSPB groups around the world including America, New Zealand and Australia.

'I know of at least 70 cases in Australia, many of which I have been involved in professionally, where I have come to the conclusion that the parent wasn't guilty,' said Dr Helen Hayward-Brown, a medical sociologist and advocate for parents whose children have been taken from them.