Harman claims Hodge, now a minister in the Department for Work and Pensions, has failed numerous parents whose children have been taken into care by councils on the basis of unfounded evidence.

She attacks as “craven, absolutely craven” Hodge’s decision to let councils investigate such cases themselves after doubts emerged about the reliability of expert evidence indicating possible child abuse.

In December 2003 Angela Cannings was cleared on appeal of murdering her three babies, who she insisted were the victims of cot death. Her conviction was overturned after evidence given by Professor Sir Roy Meadow, the now discredited paediatrician, was challenged by Cannings’s lawyers.

After she was cleared, many parents whose children had been taken into local authority care as a result of expert medical evidence hoped decisions on their cases might also be overturned. There are, however, tight legal restrictions on publicising such cases and many parents felt their plight was being ignored.

Immediately after the Cannings judgment, Harman, a family solicitor based in Canterbury, Kent, passed documents to Harriet Harman, her sister and then solicitor-general, to highlight one such case. They were also circulated to some journalists.

The documents related to a client whose daughter had been taken out of her care after a doctor diagnosed Munchausen’s syndrome by proxy, in which parents harm their children to gain attention.

Although Sarah Harman did not disclose the client’s identity, the solicitors’ disciplinary tribunal last week found her guilty of “conduct unbefitting a solicitor” and suspended her from practising for three months.

Harman insists she will continue to campaign for justice for parents who have wrongly had their children removed. She is angry that Hodge did not do enough to avert possible injustices in social services departments and the family courts.

She said Hodge’s decision to ask local authorities to conduct their own review of family court cases involving children and expert medical evidence after the Cannings case rather than set up an independent inquiry was a terrible error.

“Margaret Hodge was craven, absolutely craven. She missed an opportunity to act in the interests of children,” Harman said.

Of 28,866 child orders considered in the local authorities’inquiry that followed, only one was amended as a result of possible flawed evidence. Harman says the authorities had no interest in questioning their own judgment in cases.

Harman believes a more thorough review might have exposed “dozens or even hundreds of cases”. “The family courts prefer 20 years of tyranny to one year of chaos,” she said.

Harman believes parents are still at risk of having their children unjustly taken into care and says she will continue her campaign until “someone slaps an Asbo on me”.

Harriet Harman said she agreed with her sister’s concerns about unnecessary secrecy in the family courts. “We have a responsibility for deciding the law but it’s worrying if we can’t see how it works in practice,” she said.

“We should have a system which is more open, and this is being considered by the government.”

Cannings said last week that she supported Sarah Harman’s campaign. “She has been found guilty for what she has done but she obviously cares desperately about what is happening in the family courts,” Cannings said.

The case that Harman highlighted by circulating the court documents involved a mother who was accused of trying to harm her two-year-old child.

The mother, who cannot be named for legal reasons, is still living apart from her child after her appeal against the care order was rejected. She said last week: “I feel incredibly guilty about what has happened to her [Harman]. She has been there for me throughout.”

Hodge said Harman’s comments were “harsh” and the review by local authorities was appropriate. She said those involved in the review were not social workers directly involved in the case and it was “not helpful” to question the independence of social services.

Additional reporting: Tariq Tahir

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