A British MP has insisted a Russian woman who works for him has "nothing to hide" after she was arrested reportedly on suspicion of espionage, AFP reported.
Katia Zatuliveter faces deportation after being detained in London.
It's thought to be the first time since the end of the Cold War that someone working in Britain's parliament has been accused of spying for Russia.
The 25-year-old was arrested after British domestic intelligence agency MI5 decided she was working for the Russian intelligence service as a "sleeper" agent, the Sunday Times newspaper reported.
Liberal Democrat MP Mike Hancock, who employed Zatuliveter in the House of Commons, dismissed the spying allegations and said she was planning an appeal.
"I have no evidence ... to support the view that she is any way a threat to the United Kingdom," he told the BBC.
The politician sits on a parliamentary committee tasked with overseeing the work of the Ministry of Defence and his constituency in Portsmouth, on England's south coast, has significant naval interests.
But he insisted that Zatuliveter, who has lived in Britain for almost three years, was not working on anything sensitive.
"What on earth was she spying on?" he said.
"As far as I'm concerned, there's nothing she was doing for me which was any way sensitive."
"She is determined to fight her corner and she genuinely believes, and I back her 100 per cent, that she has nothing to hide and has done nothing wrong," he told Sky News television.
"If she has, the (security) services are right. But they need to prove their point now."
She had already been questioned by the security services in August after being stopped as she returned to Britain, Hancock said in a statement.
A spokesman for the Home Office, or interior ministry, said: "We do not routinely comment on individual cases."
The removal order came after Home Secretary Theresa May was briefed by MI5 on Zatuliveter, who was thought to be working for the SVR, Russia's foreign intelligence service, the Sunday Times said.
The SVR is the modern successor to the KGB and remains intensively active in the post-Cold War period, AFP reported.
A source cited by the paper said the Russian's presence was "not considered to be conducive to national security. There was unhappiness about what she could have access to. The intention is to show her the door".
The latest controversy over alleged Russian espionage comes after 10 sleeper agents were expelled from the United States in July.
If Zatuliveter were deported, it could place further strain on Britain's diplomatic relations with Russia.
Those relations are just starting to emerge from an icy period after the murder by poisoning of the dissident Russian spy Alexander Litvinenko in London in 2006.