The latest ruling will be made public at 2pm on 24 March - more than a month after the seven lords finished hearing evidence.

The ruling is a key decision in a case that has provoked strong feelings from both those who brand the former Chilean dictator a mass murderer and others who insist he saved the country.

Protesters have kept up a vigil outside the House of Lords

Throughout the hearings, the UK Parliament has become the focus of much of that anger, with demonstrators from both sides taking up their positions behind barricades on most days.

A previous hearing by a separate panel of five Law Lords ruled General Pinochet should be extradited to Spain, where he would face charges including torture and murder.

That decision was upheld by Home Secretary Jack Straw, who had the power to block the extradition.

But the Law Lords were forced to hold an unprecedented second hearing after it emerged one of the original judges had links to a human rights group who gave evidence.

Lord Hoffmann admitted he sat on the board of the charitable arm of Amnesty International, a fact he had not disclosed before sitting on the case.

This was judged to have presented a real risk of bias.

General Pinochet, 84, has continued to live under conditions of house arrest while the legal process against him continues.

He was arrested five months ago after coming to the United Kingdom for a back operation.

If the Law Lords rule his detention was illegal, he would immediately be free to return to Chile.

The Chilean Government has already protested about the delay in the Law Lords giving their judgement.

Presidential Chief of Staff John Biehl said earlier this week: "We have expressed our displeasure over the delay in this situation, which affects our internal affairs."

This message has been passed to the UK Government through "the proper channels", he said.

Amnesty International equally welcomed the imminent announcement.

"This is a chance to bring the international law against mass murder and torture off the statute book and into action," a spokesman said.