A young Russian woman who works for a British member of parliament and was detained by security services on suspicion of espionage said on Monday she was appealing against an order to deport her.
Katia Zatuliveter, 25, was quoted by the BBC's Russian language service as saying that she had been arrested early on Thursday and told she would be expelled.
The Sunday Times had reported she had worked for the Russian foreign intelligence service as a "sleeper" agent.
"I am in the process of appealing against the deportation and absolutely sure I will win it," she said, according to a BBC Russian transcript.
Zatuliveter had been working for Liberal Democrat MP Mike Hancock who sits on parliament's defence select committee, which examines defence policy but has no access to secret material.
Hancock, whose home district is in Portsmouth in southern England where there is a large naval base, has denied his research assistant did anything wrong.
He said his assistant, who had been employed by him for close to three years, had passed strict security vetting procedures to work in parliament.
Zatuliveter said nobody had explained to her why she had been held, "and this is my main concern".
A security source was quoted by The Sunday Times as saying that Zatuliveter's presence was not "conducive to national security", and the intention was to "show her the door".
The Sunday Times said it was the first time since the end of the Cold War 20 years ago that someone working in Britain's parliament had been accused of spying for the Russians.