The Home Office move comes in response to a request from the Chilean government for General Pinochet's release because of his ailing health.

The 83-year-old general has spent more than a year in London awaiting a decision on whether he should be extradited to Spain.

The BBC has learned that he recently suffered a further minor stroke - his third since he was detained in London.

The general's supporters hope the request will trigger his release

The latest development has been welcomed in Chile, where General Pinochet's supporters see it as a sign that the Home Office is actively involved in the case, even though strictly speaking it is a matter for the courts.

It is not known whether General Pinochet will agree to a further medical examination, but it seems unlikely he will refuse the request.

His supporters say his health is deteriorating under the stress of his battle to avoid standing trial for human rights abuses during his regime.

'Could not endure trial'

In addition to the three strokes, he is said to have been suffering from a heart condition, diabetes and depression.

A spokesman for the Chilean foreign ministry confirmed Mr Straw had asked for the further medical tests by a Home Office-appointed doctor.

Chilean foreign minister Juan Gabriel Valdes had written to Mr Straw saying the general was "in no condition to endure a long trial".

General Pinochet was excused attending last month's court hearing at which a magistrate ruled he should be sent to Spain, on the grounds that he was too frail.

The general, living in a rented mansion on the Wentworth Estate in Surrey, has already undergone a series of medical tests at local hospitals, including a brain scan.

Lamont sceptical

Former Chancellor Lord Lamont, a keen supporter of Pinochet, was sceptical about the Chilean Government's statement and said even if the home secretary was considering tests, his release could be needlessly delayed.

"I do not believe this carries us forward at all. The key question is at what point would Mr Straw make any decision," Lord Lamont said.

"Hitherto, he has only said he would do that at the end of the legal process. I will only believe there is a change when he indicates he is prepared to make a decision earlier than that.

"I think there is a lot of whistling in the dark by the Chilean Government to keep their spirits up."