Animal rights campaigners yesterday said they would fight any move by the home secretary, David Blunkett, to ban American activists from entering the UK.

The Home Office has written to a number of US campaigners, warning them that they may not be allowed in if they are deemed to have made statements inciting violence in the UK. There is no appeal against exclusion, although campaigners in the UK can seek judicial reviews of Home Office decisions.

Among those written to is Jerry Vlasak, a California-based surgeon and adviser to Speak, the group leading a campaign to halt construction of an animal research laboratory at Oxford University.

Dr Vlasak is due to appear at a conference being organised next month by Shac, the group waging a campaign against Huntingdon Life Sciences, which uses animals for research, in Cambridgeshire.

Dr Vlasak came to the attention of Mr Blunkett when quoted in the Observer last Sunday as apparently advocating the killing of scientists involved in animal research. He claims he was misrepresented.

The Home Office will not say which American activists have been written to, but Dr Vlasak told the Guardian yesterday that he was among them. He had received an email from the home secretary asking him about what he had allegedly said.

He emailed Mr Blunkett back to say that his remarks had been taken out of context. He said yesterday that he felt he had as much right to visit the UK as Nelson Mandela, to speak on the struggle against an injustice. "I have every intention to take legal advice if they do ban me," he added.

A leading light in Speak, Robert Cogswell, said: "It seems very odd that it is deemed acceptable for Dr Vlasak to treat patients in Los Angeles, but he may not be allowed into the UK to speak about animal welfare. It would set a very dangerous precedent and must be resisted."

The Home Office said the government had "sent a warning to a number of American activists that they are examining statements they have made about issues involving possible violence in the UK".

It added: "The Home Office has the right to exclude anyone it believes may be intending to cause violence or provoke violence in the UK."

The Home Office stressed that exclusion orders were not lightly issued. Last year only 15 were made.

Groups such as Speak and Shac would relish the publicity a high court case would bring. Shac has issued a "big thank you" on its website to "the media, the government and Huntingdon Life Sciences" for the publicity it and other like-minded groups received last week when the issue was high on the news agenda.

"The last 10 days have seen a massive groundswell of interest and support ... We would like to thank our enemies for making us even stronger."