The Home Office has said that former Chilean dictator General Augusto Pinochet is unfit to stand trial for human rights abuses.

Home Secretary Jack Straw is said to be "minded" to release General Pinochet - and not extradite him to face charges in the Spanish courts - after medical reports showed he was not well enough.

The Home Office said the "unequivocal and unanimous" conclusion of a four-strong medical team who examined the 84-year-old on 5 January was that he was "at present unfit to stand trial, and that no change to that position can be expected".

It added: "In the circumstances, the Secretary of State is minded, subject to any representations he may receive, to take the view that no purpose would be served by continuing the present extradition proceedings and that he should therefore decide not to extradite Senator Pinochet."

Mr Straw's decision to release General Pinochet is subject to representations from interested parties including Spain and Chile. They now have seven days to make their cases.

However, the general has refused to allow Spain or other countries with outstanding extradition requests to see the medical reports, making it difficult for them to challenge Mr Straw's preliminary decision to release him.

Baroness Thatcher, who has campaigned for General Pinochet's release since his arrest in London in 1998, said: "I would trust the Home Secretary's judgement. He is a very fair man."

The surprise announcement came after initial medical reports showed that the former Chilean head of state was fit to stand trial.

The Home Office said the new tests were ordered after an appeal by Chile in October to allow General Pinochet home on humanitarian grounds, after his health was said to be deteriorating. He is said to have suffered a series of strokes and has diabetes.

The general underwent seven hours of medical examination at Northwick Park Hospital in London by neurologists and neuropsychologists.

He was excused attending last October's hearing, at which magistrates sanctioned his extradition to Spain, on the grounds of ill health.

However, that was on the basis of medical reports from General Pinochet's own doctors.

Campaigners for his extradition have already called for a judicial review of any decision to halt proceedings.

Helen Banber, director of the Medical Foundation for the Care of Victims of Torture, said: "Any decision by Jack Straw to release General Pinochet on health grounds should be subject to immediate judicial review.

"Until such a process takes place and the medical evidence examined in court, he should be extradited to face trial in Spain."

Luis Machiavello, of Chile's Families of the Disappeared, said he respected Mr Straw but felt General Pinochet should still stand trial.

"I think General Pinochet is mentally fit to stand trial to answer the charges he needs to answer. If he is mentally fit to go back to Chile, I think he should stand trial," he told BBC News 24.

Mr Straw's decision comes hot on the heels of controversy over his handling of the case of Konrad Kalejs, the suspected Nazi war criminal.

Kalejs, who was exposed as living in a retirement home in Leicestershire, left Britain voluntarily after Mr Straw declared there was not enough evidence to detain him in the UK.