Lady Thatcher, a friend of the former Chilean dictator, renewed her fierce criticism of his arrest in a speech to a fringe meeting at the Tory conference.

But Amnesty International UK has strongly rejected her assertion that the 83-year-old's detention was a politically-motivated act prompted by left-wing opponents.

They pointed out that he was charged under international law with criminal offences of torture and conspiracy to torture.

A magistrate in London is expected to rule on Friday on whether General Pinochet should be committed to await Home Secretary Jack Straw's final decision on extradition to Spain.

The general has already been excused attendance at the hearing after the court heard he had suffered two minor strokes recently.

In her speech on Wednesday night, Lady Thatcher claimed that his arrest by British authorities, at the request of Spain, "would do credit to a police state" and amounted to "judicial kidnap".

The former prime minister went on to claim the left was motivated by a desire for revenge in arresting the general.

"Perhaps his enemies will succeed. Perhaps he will die here, as this country's only political prisoner," she told the meeting.

Torture charges

But Amnesty International's UK director Mary Robinson insisted: "Pinochet is not a political prisoner.

"He is being held because he is accused of the crime of torture, not in connection with some political offence.

Many relatives of the Pinochet regime's victims want the general tried

"Torture became a crime in the UK under the 1988 Criminal Justice Act - legislation created by a government which Margaret Thatcher led.

"Torture is explicitly not regarded as a political crime under the 1989 Extradition Act."

A Spanish investigating judge, Baltasar Garzon, has accused General Pinochet of orchestrating the brutal repression of political opponents, involving the routine use of torture, during his 1973-90 dictatorship.

An official Chilean government report found that 3,197 people were killed, or disappeared, in the years after the general toppled the democratically-elected government of President Salvador Allende in a military coup.

Judge Garzon's allegations have been refined by the Crown Prosecution Service, acting on behalf of the Spanish authorities, into 35 charges - one of conspiracy to torture, and 34 of tortures of Chilean individuals.

Mixed signals report

The CPS has declined to comment on reports from Madrid that Brian Gibbins, one of the prosecution team in the Pinochet case, has written to Judge Garzon complaining of mixed signals from Spain about whether to appeal if the magistrate in London rules the general should go free.

According to the reports, Mr Gibbins said in his letter that when he met two Spanish diplomats earlier this week, they told him their government had not yet decided whether it wanted an appeal filed if the extradition bid was rejected.

Judge Garzon wrote back, reaffirming his instructions for an immediate appeal if the ruling should go in the general's favour.