Unions representing parliamentary staff have called for MPs accused of sexual misconduct to be excluded from the Westminster estate while investigations take place, after allegations against the Conservative backbencher David Warburton. The joint call by unions representing parliamentary workers – Prospect, the FDA, the Public and Commercial Services Union and the GMB – comes after Warburton was accused of sexual harassment as well as alleged cocaine use and potentially failing to declare a loan. The MP for Somerton and Frome has denied any wrongdoing, and has been taken to a psychiatric hospital. He has lost the Tory whip and is expected to face a series of investigations over the claims. In a statement, the unions said they had written to Karen Bradley, who chairs the cross-party Commons procedure committee that examines the working practices of the Commons. They have asked Bradley to look at whether it might be practicable to introduce a rule meaning anyone being investigated over sexual misconduct is kept away from the parliamentary estate during any investigations. The idea was also proposed in a report by the Commons women and equalities committee into helping to create a more gender-sensitive parliament. Garry Graham, deputy general secretary of Prospect, said such a measure was long overdue: “We are again in the situation where an MP, accused of a serious offence, is technically free to come and go as he pleases. This is a ridiculous oversight that will leave people questioning parliament’s commitment to keeping its staff safe.” Bradley should act to “bring parliament into the 21st century as an employer,” Graham said. “In no other workplace would someone subject to such serious allegations receive only a voluntary ban.” The allegations of misconduct, made by three women according to the Sunday Times, would be investigated by parliament’s independent complaints and grievance scheme, which does not comment on ongoing cases. Warburton could also be investigated by the parliamentary commissioner for standards over a loan he received in 2017 of close to £150,000 for a holiday rental property, if this was not properly registered. The loan, which has now been repaid, was provided by Roman Joukovski, a financial adviser who specialised in offshore tax advice and providing tier one “golden” investor visas. Finally, Warburton could face an inquiry by police after media reports about the claims included a photograph of him with lines of a white powder, allegedly reported to be cocaine. The Sunday Times said two former aides to Warburton had made complaints about him, and that the fact he employs his wife, Harriet, whose role includes human resources issues, made it harder for them to take action. A cabinet minister defended the working practice of MPs employing relatives, which was banned for new MPs from 2017, saying it was “really productive”. Simon Hart, the Wales secretary, who employs his wife, told Times Radio he was a “staunch defender” of the idea. “I think that’s actually pretty insulting towards so many husbands wives and partners who do a really good job in parliament, work bloody hard, and provide the taxpayer real value for money,” he said.