Labour leader Jeremy Corbyn has vowed to scrap the so-called “rape clause” for child tax credits if he is elected as prime minister.
The Tory policy, which limits tax credits to two children with an exemption for women who have conceived as a result of rape, was introduced in April as part of wider welfare reforms. It was passed into law without a debate or vote in March.
Mr Corbyn said Conservative politicians should be “ashamed” of the “abhorrent” measure.
The rule is part of a policy restricting child tax credits to the first two children in a family. Labour branded it “an attack on low-income families” in its manifesto.
Campaigners, human rights groups and some politicians have condemned the new law.
Last month Scottish Labour leader Kezia Dugdale read aloud a powerful letter in the Scottish Parliament from a woman who became pregnant after being raped.
The woman told of how the "need to protect my children from the truth came above all other considerations" to avoid "the permanent and damaging stigma attached to rape".
Mr Corbyn said his party would "end the abhorrent rape clause across the UK."
He added: “Kezia Dugdale’s powerful speech in the Scottish parliament demonstrated the heartbreaking reality of the rape clause. Theresa May and [Scottish Conservative leader] Ruth Davidson should be ashamed of this policy. Only a Labour government that works for the many, not the few, can bring this policy to an end.”
Mr Corbyn said the two-child tax credit policy would “increase child poverty” and said he would “redesign” the law if he was elected.
The Equality and Human Rights Commission has said the policy could violate human rights laws, adding that the Department for Work and Pensions had not co mpleted a “sufficiently detailed” impact assessment before implementing the reforms .
After facing backlash, Scottish Ms Davidson said she could be open to a review of how the rape clause works.
