The Liberal Democrats have referred a rape allegation to the police and suspended a party member pending further investigation.
A party spokesman confirmed the move saying the Lib Dems have a "robust complaints procedure", but it came amid claims that the alleged offence was hushed up.
A new website called LibDemsToo was also set up, to allow people a place to set out claims of harassment they have experienced in the party.
The rape claim is the latest turn in a spiralling Westminster sexual harassment scandal, which has dragged in MPs from both the Conservative and Labour parties as well.
A Lib Dem spokesman said: "These allegations were referred to the police for investigation. A member of the party is suspended pending the outcome of that investigation.
"If an allegation is made against a party member, the disciplinary procedure is triggered immediately with an investigator talking to witnesses.
"If someone has an allegation of a criminal nature against a member of the party, we would urge them to go to the police. If they were unable to do so, we would refer it to the police on their behalf."
The spokesman said the party has "a clear and robust complaints procedure" and that it took all complaints "extremely seriously", before urging people to come forward.
But tweets from activist Sophia Nash claimed the response had been slow and poorly handled.
She claimed allegations had been made by a series of different people about the individual without action being taken.
The LibDemsToo website already has a string of testimonies from party activists setting out claims of harassment in the party.
One of them reads: "When I was 22 I was a constituency agent and organiser. After the local elections one of the male councillors (aged ~60) who had lost his election came into the office to return his polling day box and say goodbye whilst I was in a meeting. He said 'give me a hug' then whispered in my ear so that no-one else could hear, 'if I was 20 years younger…'"
On Monday morning a former Conservative activist also claimed she was ignored after raising concerns with Parliament’s authorities over an alleged rape and the “toxic” Westminster culture.
She reported that she was raped by an employee of a Conservative MP, telling the BBC: "I was raped by someone senior to me in the Conservative party. It was violent. It wasn’t in Westminster, it was in my home.
"And it shouldn’t have happened. I remember the attack, during the attack. I remember the room disappearing around me and thinking I was going to die."
Leading Labour activist Bex Bailey has also said she was raped at an event being run by her party in 2011.
Talking openly about the incident, she said: "It took me a while to summon up the courage to tell anyone in the party, but when I did, I told a senior member of staff who told me...it was suggested to me that I not report it.
"I was told that if I did it might damage me."
