An MP has denied his Russian assistant was a spy, as she could face deportation from the UK after security services arrested her on suspicion of espionage.
The Sunday Times reported that Home Secretary Theresa May had approved the removal of Katia Zatuliveter after being briefed by MI5 about her alleged activities.
Ms Zatuliveter had been working for Liberal Democrat MP Mike Hancock, who confirmed that she had been taken into detention and was fighting deportation.
The 25-year-old, who held a House of Commons pass and underwent security vetting before taking up her position, was reported to have been arrested by police and Border Agency officials last week and is understood to be being held at a secure facility awaiting deportation to Russia.
The Sunday Times reported that she was suspected of working for Russia's foreign intelligence service, the SVR.
If confirmed, this would be the first case since the Cold War of a Russian agent being removed from the Houses of Parliament.
But Mr Hancock said: "She is not a Russian spy. I know nothing about espionage, but she has been subjected to a deportation order.
"She is appealing it, because she feels - quite rightly - that she has done nothing wrong."
The Portsmouth South MP said that the security services had never raised concerns with him about the possibility that Ms Zatuliveter might be working for Russia.
"No-one has ever said to me under any circumstances whatsoever that she has been involved in anything like that," he said. "It is now in the hands of her lawyers. I am sure that in the end she will be proved to be right."
Asked about the report, a Home Office spokesman said only: "We do not routinely comment on individual cases."
It was not immediately possible to contact Ms Zatuliveter or her lawyers.