A Liberal Democrat MP who had an affair with an aide accused of being a Russian spy has resigned from his post on the defence select committee.
Mike Hancock was named during the case of Katia Zatuliveter, accused of starting an affair with him because she saw him as politically influential.
She denies spying and is fighting her deportation at the Special Immigration Appeals Commission.
Mr Hancock said the committee should be allowed to work unimpaired by the case.
The Lib Dem MP for Portsmouth South resigned in a letter to the Lib Dems' chief whip Alistair Carmichael, on Tuesday morning.
In it Mr Hancock said: "It is not appropriate for me to provide running commentary on on-going legal proceedings; however, I would like to make clear that at no time did I pass on material to Ms Zatuliveter which was not in the public domain or which was classified."
He said he hoped to resume his work on the committee once the case is concluded.
'Great deal of thanks'
Mr Carmichael said in response: "As a member of the committee for more than a decade, you have contributed to its hugely important and influential work for which you are owed a great deal of thanks.
"I understand your reasons for wishing to step down. I think that your concern in acting to protect the work of the select committee is exactly what I would have expected of you."
Government lawyers say Katia Zatuliveter should be deported on national security grounds.
On Wednesday, a deportation hearing was told MI5 only showed interest in her after Anna Chapman was thrown out of the US for spying.
Tim Owen QC, Miss Zatuliveter's lawyer, asked an MI5 agent known as "Witness ZZ", whether her interest in his client was entirely due to Anna Chapman.
The agent denied the suggestion.
Earlier, "Witness ZZ" said she knew the Chapman case, and was familiar with the FBI files on it.
Mr Owen said the fundamental difference between the cases was that the US agency had concrete evidence against Russian-born Miss Chapman, something he said UK officials did not have.
He asked: "Were there concerns among any of you about the absence of evidence that Miss Zatuliveter had done anything to harm national security? Did anyone even raise a voice and say, 'Hang on a sec'?"
The witness replied: "I am not able to confirm or deny the details of evidence in this case," but told the hearing the two Russians had similarities.
"They are both young women and both adept networkers," she said.