The Labour government has come under fresh pressure to abolish the two-child benefit limit after the latest official figures showed a record 1.6 million children were living in families affected by the controversial policy. Campaigners, charities and MPs across the political spectrum described the figures as shameful and renewed calls for the benefit limit to be scrapped, saying the much-criticised policy introduced by the Conservative government seven years ago had become the UK’s biggest single driver of child poverty. The Labour MP Kim Johnson plans to table an early – day motion on Monday that would gauge support for her intervention, and is ready to table an amendment to the king’s speech on Wednesday that is expected to appeal to a “broad church” of Labour MPs. With only days to go before the king’s speech, and Labour’s 411 MPs still being sworn in, it is unclear how many will be willing to put their neck on the line and make a clear challenge to Keir Starmer so early in the new parliament. The Liberal Democrats, who are understood to be focusing on targeting their attacks on the Conservatives, said they would scrap the policy in their manifesto, and would be likely to vote in favour of a Labour amendment. Richard Burgon, the secretary of the Socialist Campaign Group of Labour MPs, said scrapping the cap would “not only lift half a million children out of poverty, but it would also be a powerful statement of intent from my party about how this Labour government will deliver the kind of practical positive change people so desperately need”. The former shadow chancellor John McDonnell, also a member of the SCG, has joined the grassroots organisation Momentum in urging the government to ditch the policy, and has urged Labour voters to email their MP or Starmer in support of the campaign. It is unlikely the amendment would pass, but the Scottish National party and the Greens have called for the policy to be scrapped, and are understood to be prepared to hear the king’s speech before deciding whether to also table an amendment. Johnson, the MP for Liverpool Riverside, said: “Labour has a huge task to undo 14 years of Tory decay and will have to make difficult decisions about what to prioritise. But I would like to see lifting the two-child benefits cap a priority for the new government as the single most cost-effective and most impactful way to immediately alleviate child poverty in communities like mine across the country.” A number of newly appointed cabinet and junior ministers have previously voiced their concern about the cap, but many are expected to hold the line, given it is not a policy Labour wanted to enact, but they do not want to break fiscal responsibility. A total of 1.6 million children – equivalent to one in nine of all UK children – were affected by the policy last year, an increase of 100,000, the latest statistics show, while 59% of the 450,000 households hit had at least one parent in work. The policy prevents parents on universal credit claiming benefit support for any third or subsequent child born after April 2017. Currently, this means families lose out on £3,455 a year for each child affected, subjecting many to hunger and hardship. The work and pensions secretary, Liz Kendall, said it was “a stain on our society” that too many children were growing up in poverty but gave no clear sign that Labour would abolish the two-child limit. Joseph Howes, the chair of the End Child Poverty coalition, said: “If the aim is to reduce child poverty, there is no way for the new Labour government to keep this policy in place when the evidence shows that the number of children impacted is increasing year on year.” According to the Child Poverty Action Group (CPAG), abolishing the two-child limit would cost £1.7bn but would be the most cost-effective way of immediately reducing child poverty, lifting 300,000 children above the breadline and pulling 700,000 more out of extreme poverty. Alison Garnham, the chief executive of CPAG, said: “The PM came to office pledging a bold, ambitious child poverty reduction plan and there’s no way to deliver on that promise without scrapping the two-child limit, and fast. This is not the time for procrastination or prevarication – the futures of 1.6 million children are on the line.” A notorious aspect of the policy is its exemption for children born as a result of rape. Last year 3,100 mothers were able to claim full benefit entitlements having declared on official forms their child was the victim of “non-consensual conception”. The two-child policy was introduced in 2017 on the basis that cutting benefits by more than £3,000 a year for the third and each subsequent child would persuade low-income parents to get jobs. However, subsequent research has shown it has had no impact on employment levels, but is more likely to drive families into poverty. Even some Conservatives have disowned the policy, including the rightwing Tory MP Suella Braverman and the former Tory welfare minister David Freud