Sir Roy was initially struck off the medical register

The issue was debated following the case of Professor Sir Roy Meadow.

The paediatrician was struck off after giving flawed evidence at Sally Clark's 1999 trial for the murder of her sons.

The High Court previously ruled that regulatory bodies such as the GMC could not punish expert witnesses over "honest mistakes".

During the hearing, the Attorney General Lord Goldsmith said it was not up to a court to decide if expert witnesses should escape punishment.

The General Medical Council had found that Sir Roy's evidence was so flawed that he was guilty of serious professional misconduct and so he was struck off the medical register.

But the High Court over-turned the decision in February, and said the GMC should not even have pursued the complaint.

It added that, as a witness enjoys immunity when giving evidence in court, that evidence could not form the basis of a disciplinary charge

Under the ruling, cases could only be referred to disciplinary bodies by the trial judge.

'Contradiction'

The GMC believes this decision undermines its role, and that of other professional regulators, and had asked for it to be overturned by the Appeal Court.

The hearing has not focused on Sir Roy's case, but on the GMC's ability to consider similar cases in future.

The GMC says it agrees doctors should not be deterred from giving evidence, honestly and truthfully, and within their competence.

But it has concerns over the proposal to give the trial judge the remit to decide if a professional body should investigate an expert.

It also suggests the ruling contradicts its duty to investigate any complaint which could be found to amount to serious professional misconduct.

Lord Goldsmith told the hearing immunity for expert witnesses should not be an issue for the court to have to decide.

He said: "It is crucially important that expert witnesses should assist the court conscientiously and objectively, rather than being tempted to give any evidence that suits their client's case.

"To that end, the threat of fitness to practice proceedings against them provides an important check which is calculated to assist significantly in the administration of justice and also to promote public confidence in the judicial process."

Conviction quashed

Sushma MacGeoch, a leading professional negligence law specialist, said the High Court ruling had rendered regulatory bodies "toothless" against professionals acting as experts.

She said this was "a state of affairs which neither the GMC nor other professional bodies will be prepared to accept without a fight."

But Dr Stephanie Bown, of the Medical Protection Society, said: "Judges who hear expert evidence are in the best position to determine whether the conduct in court warrants referral for regulatory censure."

Professor Meadow gave evidence at the trial of Sally Clark, who was arrested in 1998 after the deaths of her two sons, Christopher and Harry.

He told a Chester Crown Court jury there was a "one in 73 million" chance of two children dying from cot deaths in an affluent family.