Boris Johnson has suggested he would discipline the source of “misogynistic” claims about Labour’s deputy leader in a Sunday newspaper article.
He condemned the claim Angela Rayner tries to distract him in Parliament by crossing and uncrossing her legs.
The Mail on Sunday said some unnamed Tory MPs had made the allegation.
Mr Johnson threatened to unleash “the terrors of the earth” on the source behind the comments if they were ever identified.
On Monday, the prime minister told reporters it was “hard to say” if there was a cultural problem in Parliament, but described the story about Ms Rayner as “the most appalling load of sexist, misogynist tripe”.
“I immediately got in touch with Angela and we had a very friendly exchange,” Mr Johnson said.
Downing Street will not be asking for an inquiry into who made the comments to the newspaper, with a source saying this was because such inquiries rarely found the person in question.
Commons Speaker Lindsay Hoyle called the “unsubstantiated claims” in the article “misogynistic and offensive” and expressed his “sympathy” for Ms Rayner.
He has arranged a meeting with the editor of the Mail on Sunday this Wednesday to discuss the article.
UK press regulator Ipso said it had received 5,500 complaints about the article and was exploring possible breaches of its code of practice.
Ms Rayner dismissed the story as a “perverted smear” that showed women in politics faced misogyny every day.
Shadow chancellor Rachel Reeves told BBC Breakfast: “This is endemic.” She added that she did not think there was a single female MP or staff member in the House of Commons who did not have their own stories of misogyny or sexism.
And Technology Minister Chris Philp said Tory MPs who hold those views could face “serious consequences” if identified.
A raft of politicians, including female Tory MPs, have also spoken out in support of Ms Rayner.
Conservative Caroline Nokes said too many female MPs of all parties had been “on the receiving end of vile articles”, while former minister Andrea Leadsom tweeted: “Really sorry Angela. Totally unacceptable comments and reporting.”
Labour leader Sir Keir Starmer said: “The sexism and misogyny peddled by the Tories is a disgraceful new low from a party mired in scandal and chaos.”
The Mail on Sunday is not commenting.
The article quoted unnamed Conservative MPs, saying Ms Rayner would cross and uncross her legs when opposite the PM at the dispatch box in the Commons to distract him.
The newspaper article said: “Tory MPs have mischievously suggested that Ms Rayner likes to distract the PM when he is in the dispatch box by deploying a fully clothed parliamentary equivalent of Sharon Stone’s infamous scene in the 1992 film Basic Instinct.”
The piece quotes one MP as saying: “She knows she can’t compete with Boris’s Oxford Union debating training, but she has other skills which he lacks.
“She has admitted as much when enjoying drinks with us on the [Commons] terrace.”
The article also described the Labour MP’s background as “a socialist grandmother who left school at 16 while pregnant and with no qualifications before becoming a care worker”.
Many MPs have since also condemned the tone of the newspaper’s reporting.
Ms Rayner condemned the article in a thread on Twitter as “gutter journalism”, and accused the sources of “spreading desperate, perverted smears in their doomed attempts to save [Mr Johnson’s] skin” amid the partygate scandal.
She added: “I won’t be letting their vile lies deter me. Their attempts to harass and intimidate me will fail.
“I hope this experience doesn’t put off a single person like me, with a background like mine from aspiring to participate in public life. That would break my heart.”
Scotland’s First Minister and SNP leader Nicola Sturgeon tweeted: “Solidarity from across the political divide to Angela Rayner on this.
“It’s a reminder of the deep misogyny women face every day.”
Liberal Democrat MP Munira Wilson described it as a “disgraceful story”, saying: “I can’t even believe it made it into print.”