Theresa May has called for a new system to complain about the behaviour of MPs after allegations of a sexual harassment culture in Parliament emerged in the wake of the Harvey Weinstein abuse scandal.

The Prime Minister has written to Speaker of the House of Commons, John Bercow, to bemoan that the current disciplinary procedure does not “have the required teeth”. She points out that contractually an MP does not have to follow the judgement passed down by the Independent Parliamentary Standards Authority.

The proposed crackdown follows Sunday paper allegations about the inappropriate behaviour of several senior MPs, including International Trade Minister Mark Garnier, who reportedly admitted he had asked his secretary to buy sex toys for him and and calling her “sugar tits”.

The Prime Minister’s letter, addressed to the Speaker and the leaders of all the major political parties, says it is “important that those who work in the House of Commons are treated properly and fairly – as would be expected in any modern workplace”. 

Her response came after the Mail On Sunday said the married minister described the incidents as “good-humoured high jinks” and “amusing conversation”. He was said to have strongly denied that they constituted sexual harassment.

The report comes after Downing Street warned on Friday that May would take “serious action” against any minister found to have acted inappropriately.

Meanwhile, former Conservative cabinet minister Stephen Crabb was reported to have admitted sending “explicit” messages to a 19-year-old woman after a job interview at Westminster.

Garnier’s former secretary Caroline Edmondson told The Mail on Sunday he had given her the money to buy two vibrators at a Soho sex shop – one for his wife and one for a woman in his constituency office.

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 Garnier 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.”

According to the paper, he said the “sugar tits” comment was part of an “amusing conversation” about the TV comedy Gavin and Stacey, while the sex toys were bought after a Christmas lunch.

“We bought some soap sets, that sort of stuff, scented candles. The vibrator shop was high jinks,” he is quoted as saying. “I hung around outside and she went into this shop. That was it.”

The Mail said Garnier had conceded that, in the current climate, his actions could look like “dinosaur behaviour”, but insisted: “It absolutely does not constitute harassment.”

In the case of Crabb, the Mail said that he had sent “explicit” messages to a 19-year-old woman he interviewed for a job in 2013, when he was a Welsh minister.

The married MP was quoted by the paper as saying he had been “foolish” but that there had been no sexual contact.

“We exchanged messages which talked about sex but none of it was meant seriously,” he was quoted as saying. “We met for coffee a few times and had a glass of wine once at the Commons, but nothing more. I accept any kind of sexual chatter like this is totally wrong and I am sorry for my actions.”

Crabb resigned last year as a cabinet minister following reports of a similar incident.

The reports come amid speculation at Westminster that at least four MPs have been caught up in various allegations of sexual misconduct.

Downing Street said such behaviour was “completely unacceptable” and urged women affected to report it to the police.

Labour leader Jeremy Corbyn warned of a “warped and degrading culture” where the abuse of women had gone unchallenged for too long.

Environment Secretary Michael Gove was forced to apologise on Saturday after a “clumsy” attempt at a joke in which he likened being interviewed by BBC presenter John Humphrys to “going into Harvey Weinstein’s bedroom”.