Theresa May has ordered an investigation into claims about the conduct of minister Mark Garnier.
Mr Garnier admitted asking his secretary to buy sex toys for him and calling her “sugar tits,” according to the Mail on Sunday.
The PM has asked the Cabinet Office to look at whether his reported actions broke the ministerial code, Health Secretary Jeremy Hunt told the BBC.
Mr Garnier did not respond to requests for a comment.
The prime minister is also writing to Commons Speaker John Bercow, calling for a new contractually-binding grievance procedure to be set up for all MPs and their staff, Mr Hunt told the Andrew Marr show.
Mrs May would also be asking Mr Bercow for his advice on how the culture at Westminster could be changed, he added.
Soho sex shop
Mr Hunt said recent newspaper reports about inappropriate behaviour by MPs and ministers were “totally unacceptable if true”.
Asked about the working culture at Westminster, Mr Hunt said: “Things have got better in recent years but there is still some way to go.
“There are mums and dads who have daughters who are politics students hoping to get a job in Westminster, and they must be able to be confident that if they get that job, their daughter will not be subject to some of these behaviours that we have been seeing.”
Asked about the idea of setting up a new body that complaints can be referred to, Mr Hunt said: “I think there is merit in the idea of having someone anonymous that you can talk to if you are unhappy about the way you have been treated.”
Mr Garnier’s former secretary, Caroline Edmondson, told the Mail on Sunday he had given her money to buy two vibrators at a Soho sex shop.
Ms Edmondson, who has since left to work for another MP, was quoted as saying that on another occasion in a bar, in front of witnesses, he told her: “You are going nowhere, sugar tits.”
The Mail reported that Mr Garnier, an international trade minister, had admitted the claims, saying: “I’m not going to deny it, because I’m not going to be dishonest. I’m going to have to take it on the chin.”
The newspaper said Mr Garnier had conceded that his actions could look like “dinosaur behaviour” in the current climate, but added: “It absolutely does not constitute harassment.”
Shadow Home Secretary Dianne Abbott told the Andrew Marr show the culture for women in Parliament had improved since she was elected in 1987, but said there was “still a long way to go”.