Rishi Sunak will be told to scrap the Tories' "cruel" two-child benefit limit during a confrontation at Prime Minister's Questions tomorrow.
The Tory leader will be tackled with "sky-rocketing" child poverty during the session as his party continues to trade bitter blows over ex-PM Boris Johnson's peerages list.
The Labour MP Kim Johnson, who will raise the issue on Wednesday, told The Mirror the two-child cap - first unveiled during the austerity years - is "as cruel as it is ineffective".
Under the controversial policy Universal Credit is restricted to the first two children in a household if they were born after April 2017, with some exceptions.
Ms Johnson said scrapping the measure would be the "single most effective intervention to tackle child poverty" with the "evidence there for all to see".
She added: "Punishing families for having more than two children doesn’t push parents back into work – it only drives more children into poverty.
"Tory austerity cuts were nothing less than an ideological drive to rig the economy in favour of the few at the expense of the many.
"And children in my constituency and across the country are now paying the price."
With the Bishop of Durham in the House of Lords, the Labour MP for Liverpool Riverside has also sponsored a Private Member's Bill aiming to remove the two-child benefit limit.
The Bishop told The Mirror: "The two-child limit is currently the greatest contributor pushing families and children into poverty in the UK.
"My hope is that this Bill will change that, allowing thousands more children to grow up free from poverty, their life chances no longer limited by the number of siblings they have."
Their remarks come after the Shadow Work and Pensions Secretary Jonathan Ashworth signalled an end to the "heinous" policy if Labour wins power at the next election.
The Labour frontbencher said: "The former Conservative welfare minister David Freud described this as a vicious policy. He was absolutely correct to describe it as a vicious policy."
According to the End Child Poverty group 4.2million kids were living in poverty between 2021 and 2022 and have called on ministers to scrap the two-child policy.
The Government has previously defended the policy, however, saying it "means families on benefits are asked to make the same financial decisions as families supporting themselves solely through work".
"There are careful exemptions and safeguards in place within the policy to protect people in the most vulnerable circumstances," it added.
