DNA paternity and maternity tests cannot be relied on, says top judge

He also identified problems with key evidence in more than 120 hearings in the courts, raising fears that children may have been wrongly removed from their parents.

The public and Press are normally banned from proceedings in the Family Court, with parents gagged from talking about its findings even if they believe they are the victims of a miscarriage of justice.

But Deputy High Court Judge Anthony Hayden QC took the unusual step of publishing a judgment after a series of errors came to light in one case of abused children.

Only five laboratories are Government-certified for court work. But a loophole allows lawyers to hire uncertified scientists unless a judge makes a specific order compelling them to use approved labs.

The problem was highlighted in a case before Judge Hayden in December - when lawyers hired Liverpool-based DNA Diagnostics. Despite regularly giving evidence, it is not Government-approved.

The case involved eight children - victims of physical, emotional and sexual abuse - who had been looked after by several adults in two households.

Their abuser had been identified and sentenced in a criminal court, and the Family Court had to decide if the children, who had been put into care, should be returned to their parents.

According to the judgment, the firm lost photographs required to confirm the chain of evidence - then tried to carry out new tests on the youngsters without permission from the judge.

Then a lawyer in the case said that "she had been in a case recently where an identical problem had arisen with this same firm", Judge Hayden said.

"On that occasion she had received a bouquet of flowers ... by way of apology."

DNA Diagnostics confirmed the lawyer's claim and admitted it had lost similar material in a further 122 cases. It repaid £6,000 in fees for the case in Judge Hayden's ruling.

He accused the firm of a "systematic failure", adding: "The procedural and professional deficiencies that have been identified ... would have made it quite impossible for any court to rely on its [DNA Diagnostics'] conclusions."

Judge Hayden also questioned a second laboratory in the case.

He said Anglia DNA, which is approved by the Ministry of Justice, alleged there was an incestuous relationship in the case, only to withdraw the claim after a third firm's analysis that "flatly contradicted" this assessment.

Anglia DNA blamed unclear instructions from a lawyer.

Due to the secrecy around the Family Courts, it is unclear if people in other cases have been informed of the problems, or if it has led to any appeals.

House of Commons Justice Committee chairman Alan Beith MP said: "This is very serious. Errors mean children could be taken from their parents when they shouldn't be."

Last night, the Ministry of Justice said there was no need to change the law to compel lawyers to use only approved firms. A spokesman said: "The civil courts already have the power to give direction to ensure a laboratory is chosen from the accredited list."

DNA Diagnostics said it had addressed the problems identified and had now applied to join the approved list.