Belgium has defended its efforts to stop General Augusto Pinochet returning to Chile following strong criticism in the High Court.

Six human rights groups have joined Belgium in seeking a judicial review of Home Secretary Jack Straw's statement that he is "minded" to allow the former Chilean dictator to return home on health grounds.

The legal moves come as the home secretary revealed that General Pinochet's stay in the UK had already cost the taxpayer £1.3m.

The Belgian letter requesting the results of the medical examination that suggested General Pinochet was too ill to stand trial had been described in court as a "diatribe" against Mr Straw's decision.

But Presiley Baxendale, QC, said the request was legally justified as Belgium was one of the states seeking his extradition.

She said there had been a failure to give Belgium proper opportunity "to make comments on a proposed decision which has very important consequences for Belgium's position".

Belgium entered the dispute after allegations that General Pinochet was behind the jailing and killing of Chileans whose relatives now live in Belgium.

'Breach of natural justice'

The High Court judge has said he will give his judgment on whether the parties can ask for a judicial review of Mr Straw's stance on Monday.

Mr Straw has insisted he cannot disclose details of the medical report because they are covered by the rules of medical confidentiality.

But keeping General Pinochet's medical tests secret breaches natural justice, the High Court was told on Wednesday.

Richard Drabble, QC, for the human rights groups, said if Mr Straw did not have the power to force General Pinochet to undergo further medical tests, he could push him towards more openness.

Jonathan Sumption, QC, acting for the home secretary, insisted the laws of the country invested the authority for sanctioning extradition with Mr Straw.

He said: "The home secretary is perfectly aware of the gravity of the crimes alleged against Pinochet, but his impartial judgement in these matters is a most important safeguard for the accused and the interests of justice generally.

General Pinochet will remain under house arrest on the Wentworth Estate in Surrey until the matter is resolved.

He has been fighting extradition to Spain since he was detained in London more than a year ago.

Belgium is one of three countries, along with France and Switzerland, that filed extradition applications in the wake of the Spanish request.

A plane sent from Chile to bring the general home is still in Bermuda, awaiting a final decision.