"Mr.Krishnakumar, 31, a Central Committee member of the Liberation Tigers of Tamil Eelam - the Tamil Tigers- has been given until tomorrow to leave the country voluntarily, or face possible detention and expulsion to Sri Lanka,where his movement is fighting a bitter civil war against the governing Sinhalese majority.

Mr. Krishnakumar led Tiger forces in the northern stronghold of Jaffna under the nom de gerre of 'Commander Kittu', until he lost a leg in fighting. He was allowed to come to Britain in October 1989 for treatment, and had a number of extensions of his stay on medical grounds.

Last August, Mr.Krishnakumar sought political asylum in Britain, but was told last week that the Home Secretary, Kenneth Baker, was "minded to refuse" the application, because the Tiger leader did not have a well founded fear of persecution if he was returned to Sri Lanka.

At the same time he was informed that a deportation order had been issued against him in support of "the international fight against terrorism".

Under the 1971 Immigration Act, Mr.Krishnakumar has no right of judicial appeal against the deportation order, but can make representations to a panel of advisers appointed by the Home Secretary. The procedure, which was heavily criticised when used against alleged Iraqi sympathisers during the Gulf war, does not allow the person facing expulsion to learn the evidence against him, or to have a lawyer with him when he appears before the advisory panel. Nor is he entitled to know the panel's recommendations.

David Burgess, a leading immigration solicitor acting for Mr.Krishnakumar, said it was extremely unusual for the authorities to announce in advance that they were considering detaining some one regarded as undesirable. "If he is a dangerous person, why is there a timetable for him to remain at liberty?" asked Mr.Burgess.

Yesterday, Anton Rajah, the Tigers spokesman in Britain, denied the claims against Mr.Krishnakumar, saying that he had engaged purely in political activity aimed at promoting a peaceful settlement in Sri Lanka.

The government's denial that Mr.Krishnakumar faces persecution in Sri Lanka contrasts with its decision last month to freeze aid to Colombo and restrict arms sales in protest at the country's human rights record. The move was in retaliation for the Sri Lanka's expulsion of the British High Commissioner, David Gladstone, in May which Britain said was due to his criticism of human rights violations.

With relations between London and Colombo still cool, some sources believe Mr.Krishnakumar's deportation might be due more to pressure from India, which has accused the Tamil Tigers of responsibility for Rajiv Gandhi's assassination near Madras in May. Since then large numbers of Sri Lankan Tamils have been detained, and many face forcible return to their homeland.