Britain is being asked to carry out new medical tests on former Chilean dictator General Augusto Pinochet, to determine whether he is truly unfit to stand trial.

Spain's foreign ministry said it had forwarded a petition from Judge Baltasar Garzon, who secured General Pinochet's arrest in London in October 1998.

Mr Garzon says he wants new medical tests to be carried out by doctors of his choice, and also wants to question General Pinochet.

Results of the medical tests carried out in the UK have not been made public, angering human rights lawyers who argue they have no way to mount an effective challenge the report without knowing its details.

Mr Straw says any decision to release details of the report is up to Gen Pinochet's lawyers.

Mr Garzon has been trying to bring the 84-year-old general to Spain to face charges of human rights abuses during his 1973-1990 rule.

Declared unfit

The UK Home Secretary Jack Straw said last Tuesday he was "minded" to let the former dictator return to Chile in seven days' time.

Mr Straw's move came after a team of independent medical experts said the general was unfit to be extradited to Spain.

With the deadline for submissions to the Home Office on the subject due to expire at 1700GMT on Tuesday, several groups say they plan to oppose the decision.

France has said it will forward a request from a French judge who wants to question Gen Pinochet, and Belgium has said it too plans to push ahead with attempts to extradite him.

In a statement on Monday, the Spanish foreign ministry said it had reaffirmed the Spanish Government's decision that it would not present any appeal against Mr Straw's ruling.

The Spanish Government has insisted it has met all its legal requirements by sending Mr Garzon's requests to Britain through diplomatic channels.