The government’s chief whip, Mark Spencer, has defended his decision not to take action against an MP who has been arrested on suspicion of rape, after the alleged victim revealed she had complained about abusive behaviour four months earlier. Pressure is growing on the Conservatives to withdraw the whip from the former minister – suspending him from the parliamentary party – while the police investigation is ongoing, but Spencer indicated he would not do so. The chief whip has been criticised for failing to make inquiries after he spoke to the woman who made the complaint four months ago, after which she claimed no action was taken. Spencer has resisted calls to remove the whip from the MP, who was arrested over the weekend. “They are very serious allegations and we do take those allegations very seriously,” he said. “I think it is down to the police to do that thorough investigation, not for the whips’ office to investigate this alleged crime, it is for the police and the authorities to do that. Once they’ve come to that conclusion, then we can assess where we’re at and the position that the MP find themselves in.” One senior female former minister said the delay showed the system was “still not working for victims” while adding that it was crucial no action could be taken which might lead to identifying the complainant. “Parliament has made progress since 2017 but clearly we still don’t have the type of system that is needed,” she said. Amy Leversidge, the assistant general secretary of the FDA union, which represents parliamentary staff, called it “an astonishing decision” not to suspend the MP. “In any other workplace it would be an entirely proportionate and reasonable decision by the employer to suspend the individual to allow an investigation to take place,” she said. “This is not about guilt or innocence at this stage, it is about a duty of care to everyone involved.” The complainant, who is in her 20s, has since contacted the police, alleging rape, violent sexual assault and coercive control by the MP, who has not been named. She reported four incidents, alleged to have taken place between July 2019 and January 2020, in Westminster, Lambeth and Hackney. She alleged the MP assaulted her, forced her to have sex and left her so traumatised that she had to go to hospital. He was taken into custody in east London early on Saturday and released on bail to a date later this month. Spencer has denied the woman made any allegations of a sexual nature in his conversation with her. But he acknowledges she reported “abusive behaviour and threats”. He also advised her to go to the independent complaints and grievance scheme (ICGS). A fellow Conservative MP also raised the woman’s allegation with Spencer and Jacob Rees-Mogg, the leader of the House of Commons, after speaking to the alleged victim a month ago. Rees-Mogg did not speak to the woman, but encouraged the fellow MP to advise the alleged victim to go to the police, sources said. Speaking on BBC Radio 4’s Today programme, the business minister, Nadhim Zahawi, was asked why Spencer had not acted. Zahawi said people would be “hearing from the chief whip” only after the police investigation was over. He said: “I think it’s only right that we wait for the police to complete their investigation. As has sometimes happened in these cases – and they are very, very serious cases – when the information is finally in the public domain people realise why people have behaved in a particular way.” He declined to give any more information, or to say whether he knew about Spencer’s conversation with the woman. He also declined to say why the Conservative whip had not been withdrawn from the MP. Labour’s shadow domestic violence minister, Jess Phillips, said on Sunday she found it “shocking” that the whip had not yet been removed. “In any other organisation, were this investigation to be going on, this police investigation, somebody would be suspended while the investigation was taking place,” she told Times Radio. In an interview with the Times a week ago, the former parliamentary aide who made the allegations said she had told Spencer she had been sexually assaulted and then threatened by the MP. She told the paper: “He never suggested I should go to the police. In fact I asked him when he would withdraw the whip, he first said when he had a police report, then changed it to a charge, then he said ultimately he’d need a conviction.” The Metropolitan police said detectives had launched an investigation following the allegations, which were received on 31 July.