Sadiq Khan has said he wants to see the two child benefit cap scrapped “as soon the Labour Government can”.
The London mayor was however careful to avoid aligning himself with rebel MPs who voted against the Government over the issue in a debate on Tuesday evening.
Mr Khan said MPs who are concerned about changing the policy should instead “feed into” the Government's Child Poverty Taskforce - a review set up by ministers last week.
The cap, introduced under the Conservatives in 2017, prevents almost all parents from claiming Universal Credit or child tax credit for more than two children.
MPs voted on Tuesday on an SNP amendment which expressed regret that abolishing the cap is not in the King's Speech, arguing that the policy is pushing children into poverty.
MPs rejected the SNP amendment by 363 votes to 103, in the first major test of the new Labour government’s power.
Seven Labour MPs had the whip suspended for six months after voting against the government on an amendment.The Government has said it is not prepared to make “unfunded promises” by abolishing the cap.
Speaking to the Standard last year, the mayor said the policy “should be changed” and that he would be “lobbying the Labour team” over the issue, while insisting that “the Tories’ mismanagement of our economy” had made it difficult for his party to “automatically promise a reversal”.
Asked on Tuesday, ahead of the vote, how soon the cap should be scrapped, Mr Khan said: “There’s going to be a budget later on this year. It’s really important that Rachel Reeves asks the OBR [Office for Budget Responsibility] to look into her Budget and the figures this autumn.
“As soon as the Labour Government can, I want them to do so. But I fully support this review that Bridget [Phillipson, Education Secretary] and Liz [Kendall, Work and Pensions Secretary] are leading on.”
The mayor was speaking to journalists in Greenford at the opening of London’s first ‘multibank’ - an initiative run by the Felix Project charity and supported by Amazon, former Prime Minister Gordon Brown and the Greater London Authority (GLA).
The scheme will help around 40,000 Londoners by giving out more than 400,000 surplus essential goods, such as toiletries and bedding, over the next 12 months.
“One of the points I made today was [that] when Gordon Brown was Chancellor, and then Prime Minister, we lifted 600,000 children out of poverty,” said Mr Khan.
“Over the last 14 years, more than 700,000 children have gone into poverty. So I welcome the taskforce… Today’s vote in the Commons is an opposition day debate motion from the SNP. I’m less worried about that.
“I’m more worried [about] - and concerned, and I’ll be feeding into - the taskforce review being conducted by Bridget and Liz, because it’s not just about one thing. There needs to be many things done to first address child poverty, and then reverse it.”
Mr Khan was asked at Mayor’s Question Time last week, by Liberal Democrat assembly member Hina Bokhari, whether he would directly contact the Government to demand that the cap be removed.
The mayor avoided answering the question, instead accusing Ms Bokhari of showing “chutzpah”, as he branded the Lib Dems the “co-architects of austerity”, who “should be ashamed of themselves”.
The cap does not however date from the era of the Conservative-Lib Dem coalition, and was instead first put forward in the summer Budget after the 2015 election.