Boris Johnson has told MPs the Government's so-called "rape clause" is an "injustice" which needs rectifying.
The Prime Minister surprised onlookers in the Commons with his remarks given the Government has staunchly defended its policy, which is connected to 2017 reforms to limit tax credits to a family's first two children.
A clause in the rules means women who have a third child as a result of rape can be exempted – but would have to provide evidence to do so, a move fiercely criticised by campaigners.
— Alison Thewliss (@alisonthewliss) March 11, 2020
Speaking at Prime Minister's Questions, Labour leader Jeremy Corbyn said: "The Prime Minister supports the absolutely horrendous rape clause in the child tax credit rules.
"Why does he think it's right that 200 mothers have to prove to the Government their child was conceived as a result of being raped so they can keep their child tax credits?"
Mr Johnson, in his reply, said: "On his point about the recipients of benefit, he draws attention to an injustice and we will do everything we can to rectify it."
Mr Corbyn responded: "I hope that means the Prime Minister is going to introduce regulations to end the two-child policy in the benefits strategy because that is exactly what happens when women who are victims of rape have to prove they've been raped in order to get benefits for their child."
Ministers have repeatedly faced calls to abandon the policy of limiting tax credits to a family's first two children.
SNP MP Alison Thewliss, a long-term campaigner to end the "rape clause", wrote on Twitter: "My guess is he doesn't know what he's talking about. The two-child limit and the rape clause stigmatise, impoverish and must be scrapped."
Mr Corbyn also raised concerns over life expectancy rates for the poorest women in society, funding to tackle domestic abuse and called for Mr Johnson to apologise for his "offensive" comments about women.
On life expectancy, Mr Johnson said it has increased overall before adding: "It is absolutely true that there are too many instances and too many parts of the country where we are seeing life expectancy not rise in the way we would like, and it's true there are parts of this country where one in 50 pregnant women are smokers and parts of the country where one in four pregnant women are smokers.
"What we want to see is a uniting and levelling up across this whole country."
Mr Johnson went on to defend the Government's health funding.
In his final comments, Mr Corbyn said: "The Prime Minister has made repeated offensive remarks against single mothers and their children. He described them as ill-raised, ignorant, aggressive and illegitimate.
"Against Muslim women, saying they looked like bank robbers. Against working women, suggesting the best way of dealing with advice from a female colleague is just to 'pat her on the bottom and send her on her way'.
"Words have consequences. His offensive words are backed up by offensive and discriminatory policies, from the rape clause to dismantling local services which women, particularly BAME and disabled women, disproportionately rely on.
"Can the Prime Minister apologise for his offensive comments and ensure that these discriminatory policies are reversed by his Government?"
Mr Johnson said he is "proud" of the Government's record to promote the rights of women, of the number of female MPs in his party and the fact the Conservatives have had two female prime ministers.
He said of Labour: "Wouldn't it be an extraordinary and amazing thing if that party were to produce a female leader of their own? Don't hold your breath, Mr Speaker.
"I will take no lessons in sexism from a party where good female MPs are bullied out of their party just because they had the guts to stand up against the climate of anti-Semitism in the Labour Party."