A campaigner against forced marriage says she was promised a peerage if she slept with a senior member of the House of Lords.
Jasvinder Sanghera has disclosed that she is the woman who made a complaint against Lord Lester of Herne Hill.
She said she had waived her anonymity in an interview with the Times to encourage other women to speak out about harassment.
Lord Lester says Ms Sanghera's allegations are "completely untrue".
The 82-year-old Liberal Democrat peer, a prominent lawyer, is facing the longest suspension in modern parliamentary history, following a report by the Lords' Privileges and Conduct Committee.
The committee says Lord Lester, who played a prominent role in drafting many of the UK's human rights and sex discrimination laws, had groped Ms Sanghera and offered her "corrupt inducements to sleep with him".
Peers are expected to vote on Thursday whether to accept the committee's recommendation that he should be suspended until June 2022.
Ms Sanghera, 53, who was not named in the committee's report, told the Times she had made the complaint against him to establish that "what he did to me wasn't acceptable and wasn't honourable".
She said: "There needs to be a system in place that will give other victims the confidence to complain and to feel supported in doing so."
The alleged incidents happened in 2006, when she was working with Lord Lester on a law to make forced marriage a civil offence.
She said the peer had offered her a bed for the night at his home after she had missed her last train. She told the Times he had groped her and chased her around his kitchen when she spurned his advances.
Days later the peer told her that if she slept with him he would make her a baroness "within a year", but if she refused he would ensure she never gained a seat in the Lords, she told the newspaper.
Ms Sanghera, the founder the charity Karma Nirvana who was made a CBE in 2013, told the Times that Lord Lester's conduct "made me feel physically sick".
"I was acutely aware of the power imbalance. If I'd said anything, who would believe me?" she said.
She finally lodged a complaint in November 2017 and said the rise of the #MeToo movement led her to hope that "by speaking out, victims were creating a climate in which people were more willing to listen".
Lord Lester said the investigation was "flawed" and he had "produced evidence which clearly demonstrated that what I was said to have done 12 years ago did not happen".
Lord Pannick QC, a friend and colleague of Lord Lester, said: "It is impossible fairly and effectively to decide on the truth of allegations of sexual harassment said to have occurred nearly 12 years ago without allowing for the cross-examination of the complainant.
"The commissioner refused to allow Lord Lester to cross-examine and the commissioner failed herself to carry out that function.
"Such a process would not be acceptable in any other regulatory, disciplinary or employment context. Parliament has applied a procedure that would be invalidated by the courts if Lord Lester were to be suspended by his local darts club."
But Ms Sanghera's lawyer David Hooper said Lord Lester had previously defended the Lords' disciplinary procedures, when other peers were being recommended for suspension in 2009.
"This is the procedure that has been chosen by the House of Lords," he told BBC Radio 4's Today programme.
"They wanted their own internal discipline. They didn't want the courts to start ruling on whether peers had or had not behaved properly."