Figures published today show that a total of 1.6 million children are now affected by the two-child benefit cap.

The Conservative government introduced the cap, which prevents parents from claiming child tax credit or Universal Credit for more than two children for those born after April 2017.

It means families cannot claim about £3,200 a year per extra child, the Resolution Foundation has said – and experts say it pushes many children into poverty.

Despite having said he won’t, Sir Keir Starmer is under vast pressure to scrap the cap from both inside and outside his party.

Speaking to broadcasters, Lib Dem leader Sir Ed Davey said: “The quickest way to reduce child poverty, the most efficient, the most cost-effective way to get rid of the two child limit.”

“I hope the government listens to Liberal Democrat arguments and to those who are experts in this to make sure that we can have a fairer society and that we can dramatically reduce child poverty.”

Asked if he will try to force the issue by laying an amendment to the King’s Speech next week, Sir Ed replied: “Let’s see what happens in the King’s Speech.

“We’ve made our arguments. We think we’ve won the argument.”

Pushed on the question, he added: “We believe that the strength of our arguments are so good that the government will be forced to listen.”