A last-ditch legal battle over the fate of General Augusto Pinochet is under way in the High Court.

Belgium and six human rights groups have renewed their legal attack on Home Secretary Jack Straw's decision that he is "minded" to let Pinochet return home to Chile.

In a second High Court bid for judicial review - this time before three judges - the Belgian government accused Mr Straw of going wrong in law and acting unfairly towards a European neighbour.

Nigel Pleming, QC, appearing for the Belgians, said the Home Secretary had denied a "friendly" country the opportunity of "challenging or supporting" his stance by refusing to disclose details of the medical report on the former dictator.

The document prompted him to declare that Pinochet was unfit to stand trial on torture charges and therefore should not be extradited to Spain. Belgium has joined Spain, France and Switzerland in indicating they want to extradite Pinochet to stand trial.

Last week, Mr Justice Maurice Kay threw out the first Belgian application for judicial review when he ruled that Mr Straw had acted "lawfully, fairly and rationally" in refusing to disclose the confidential medical report.

Plane on standby

Returning to court on Monday, the Belgian legal team asked three senior judges to rule that the Home Secretary had acted in breach of natural justice.

Mr Pleming said Mr Straw had also acted contrary to international conventions to which both Belgium and the United Kingdom are parties.

Jonathan Sumption QC, for the Home Secretary, confirmed that if Mr Straw did drop the extradition case, the Solicitor General and Director of Public Prosecutions would also be obliged to consider mounting domestic action against Pinochet.

He acknowledged action was "somewhat unlikely" if the extradition case was dropped on health grounds.

Mr Pleming said: "Maybe if Belgium was permitted to see the report it will agree with the conclusions of the Home Secretary."

But to regard the report as "faultless and unassailable" was going too far, he said.

The doctors had found that Pinochet was medically unfit to stand trial and was not feigning his condition.

House arrest

Lord Justice Simon Brown, Mr Justice Latham and Mr Justice Dyson are expected to spend the next day-and-a-half hearing the case and hope to give their ruling later this week.

The 84-year-old general has been fighting extradition to Spain since he was arrested more than a year ago after coming to the UK for medical treatment.

Mr Straw has undertaken not to make a final ruling until the matter has cleared the courts.

But if the action fails, the general could be given the green light to leave the country within a matter of hours.

A Chilean jet is on standby at RAF Brize Norton waiting to take the general home if he is released. Meanwhile, he is expected to remain under house arrest at the Wentworth Estate in Surrey.

However, any triumph secured by the general may be soured by a decision last week by a Chilean judge to accept a new lawsuit against the general based on torture charges.

A group of 643 ex-political prisoners in Chile filed the suit with judge Juan Guzman in Santiago last week.

But many human rights advocates say a trial in Chile is unlikely because Pinochet has parliamentary immunity as a life senator.

The human rights groups involved in the current court case are Amnesty International, Human Rights Watch, the Redress Trust, the Association of Relatives of the Disappeared, Justicia and the Medical Foundation for the Care of Victims of Torture.