THE British Home Office is trying to renege on an assurance given to Hongkong legislators that British Hongkong nationals would be able to enter the United Kingdom after 1997 in a worst case scenario. A Legislative Council delegation visiting London early last month was told by Home Secretary Michael Howard that if British Hongkong nationals were forced to leave the territory and had nowhere else to go, their cases would be considered sympathetically. According to legislators, Mr Howard made it clear to the delegation, led by independent, Emily Lau Wai-hing, that the assurance did not just apply to the territory's 7,000 ethnic minorities. It was also applicable to the 3.2 million British Hongkong nationals in the territory. Home Office officials are understood, however, to have changed their minds and want to qualify the assurance that it would only apply to ''solely British nationals''. The difference between ''solely British nationals'' and ''any British nationals'' is that the former will not apply to British National Overseas (BNO) passport holders who are regarded by China as Chinese nationals. Intensive lobbying by Home Office officials to secure support from the Governor Chris Patten and the British Foreign Office to fudge the assurance is understood to be under way. Although Miss Lau wrote to Mr Howard last week requesting confirmation of the content of their June meeting, including the undertaking, the Home Office has delayed replying. The subject is understood to have been raised when Mr Howard met Mr Patten in London on Wednesday. Home Office officials wanted to secure the Governor's support for their case before replying to the legislators. Miss Lau last night vowed to fight hard on the subject and expected a big row if the Home Office reneged. ''I hope the Governor has not supported them [the Home Office],'' she said. ''There has been a suggestion that I tricked the Home Secretary. It's just nonsense. How can I trick the Home Secretary into things he did not want to say?'' Miss Lau believed that the British Government was afraid of offering such an open-ended commitment to several million Hongkong people. But she stressed that legislators were determined that the assurance should not be confined only to the territory's 7,000 ethnic minorities. ''We expect any British government to stand by this undertaking,'' she said. The issue may develop into a major controversy in the British parliament. The British Government has been trying hard to avoid allowing massive number of Hongkong Chinese a chance to be admitted to the UK. Another Legco delegation member, James To Kun-sun, said it was clear to all those present at the meeting that Mr Howard did offer the assurance that it was applicable to all. Mr To warned the British Government to be careful in considering reneging on the assurance. The legislature could reopen the whole subject of Hongkong people's right of abode in the UK. Another delegation member, Howard Yound, said that the assurance covered a hypothetical situation.