A member of the House of Lords should be suspended for sexually harassing a woman and offering her "corrupt inducements to sleep with him", the Lords Privileges Committee has said.
The committee recommended a suspension of Lord Lester of Herne Hill until 2022, which would be the longest in modern parliamentary history.
The House of Lords will debate a motion to suspend Lord Lester on Thursday.
The 82-year-old peer described the allegations as "completely untrue".
But the Lords Standards Commissioner upheld the complaint - which is judged on the balance of probabilities - "on the basis of the strong and cogent evidence of the complainant and her witnesses".
Lord Lester is currently suspended by the Liberal Democrats.
'Abuse of power'
In its report, the committee said a complaint had been received in November 2017 that Lord Lester "had sexually harassed the complainant, had offered her a corrupt inducement to have sexual relations with her, and had warned her of unspecified consequences if she did not accept his offer".
It added: "These allegations were connected to Lord Lester's conduct of his parliamentary duties."
The report also said Lord Lester had admitted telling another peer the name of the complainant and that she had been responsible for him being suspended by his party. This was a breach of confidentiality rules, it said.
A separate report by the Sub-Committee on Lords' Conduct, which looks at appropriate sanctions, recommended he should be expelled from the House of Lords, saying the "allegations taken together constituted a grave abuse of power".
After an appeal by Lord Lester, the committee agreed with the commissioner's verdict but changed the sub-committee's recommended sanction from expulsion to suspension.
In a statement, Lord Lester said: "I produced evidence which clearly demonstrated that what I was said to have done 12 years ago did not happen.
"Independent counsel who previously advised the committee on its procedures provided an advice which concluded that the investigation was flawed. I regret the committee's conclusions in the light of these materials."
He called for reform of the procedure for investigating sexual harassment claims, adding: "I hope to be judged by my work over decades for gender equality, race relations and free speech."
A Liberal Democrat spokesperson said: "Anthony Lester has been suspended from the Liberal Democrats and is no longer a member of the Liberal Democrat group in the House of Lords."