MPs are to vote on whether they support scrapping the two-child benefit cap, as the government faces growing pressure to get rid of the policy.

An SNP proposal – known as an amendment – expresses regret that abolishing the cap is not in the King’s Speech, arguing the policy is pushing children into poverty.

A similar amendment from Labour backbench MPs was not selected for a vote but some could choose to back the SNP proposal instead.

As the government has a large majority of 174 there is no chance it will lose the vote. But it is an opportunity for some of Labour’s own MPs to make clear their opposition to the policy and put further pressure on the government to lift it.

The cap, which was introduced under the Conservatives in 2017, prevents almost all parents from claiming Universal Credit or child tax credit for more than two children.

Labour’s landslide election victory has led to renewed calls from anti-poverty charities for it to be scrapped, with Scottish Labour leader Anas Sarwar and Greater Manchester mayor Andy Burnham also backing calls for a change.

However, the government has said it is not prepared to make “unfunded promises” by abolishing the cap.

Prime Minister Sir Keir Starmer said there was “no silver bullet” to end child poverty but acknowledged the “passion” of Labour MPs on the issue.

The SNP amendment has been signed by 21 MPs – including some from Plaid Cymru, the Green Party, the SDLP, the Alliance Party and three independents, including former Labour leader Jeremy Corbyn.

However, some backbench Labour MPs could also choose to vote in support of the move.

A vote is expected at 19:00 BST, at the end of the debate on the King’s Speech, which set out the government’s priorities for the months ahead.

Labour’s former shadow chancellor John McDonnell said he would back the SNP amendment.

In a video posted on X, he said: “I don’t like voting for other parties’ amendments but I’m following Keir Starmer’s example as he said put country before party.”

Kim Johnson and Rosie Duffield are among 19 Labour MPs who signed another amendment on the issue.

On Monday, Ms Johnson, who has led Labour calls for the policy to be scrapped, said the government to set out a “clear timetable” for doing this.

“It’s not a question of whether we can afford vital policies to alleviate child poverty, such as lifting the two-child cap, it’s a question of whether we can afford not to,” she said.

“This punitive policy needs to be consigned to the dustbin of history where it belongs.”

SNP Westminster leader Stephen Flynn said: “Keir Starmer must not fail his first major test in government by refusing to scrap the cap. It is the bare minimum required to tackle child poverty – and to begin to deliver the change that people in Scotland were promised.

“Labour MPs have a choice today. They can lift children out of poverty by voting for the SNP amendment to abolish the cap – or they will push children into poverty by keeping it in place.”

Work and Pensions Secretary Liz Kendall said the government could not tackle the “dire inheritance” from the Conservatives overnight.

However, she said Labour was “determined to make a huge difference” on tackling childhood hardship.

The Institute for Fiscal Studies think tank has estimated that removing it would eventually cost the government £3.4bn a year, roughly 3% of the total budget for working-age benefits.