Sadiq Khan has said he wants his year-long programme of free meals for primary school children to become permanent - though he stopped short of committing to that.
But he said that he would not make promises to Londoners he could not keep.
“I’d rather under-promise and over-deliver, than the other way round,” said Mr Khan.
“I have found the money for this emergency one-off funding, because of the cost of living crisis.
“We are going to be assessing the success or otherwise of this policy over the course of the year, in relation to attainment, attendance, productivity, in relation to health benefits, impacts on families, and so forth.
“In an ideal situation, of course I want this to be permanent.”
The Labour mayor’s Conservative opponent in next year’s mayoral election, Susan Hall, has said that, if elected, she would ensure the programme “continues for as long as the cost of living situation requires it”.
Mr Khan accused the party of “audacity”, pointing out that they voted against his budget this year, which included within it the free school meal programme.
Mr Khan added: “Why doesn’t she [Hall] use the powers she has, and the connections she has, to lobby her Government, who for the last 13 years have led [us] to a situation where our schools are literally crumbling - not content with public services crumbling, and austerity.
“She was the person that supported Liz Truss’s mini-budget, which has led to some of these problems, and I really don’t need any advice from her.”
In July, Labour leader Sir Keir Starmer refused to commit to introducing a similar programme of free school meals across England, if the party wins the next general election, saying “the money is a big factor”.
The mayor said in response to this point: “I fully understand why the Labour Party 18 months before a general election - there’s an autumn statement, there’s another budget, another autumn statement - simply don’t know how bad the books are going to be in 18 months’ time, should they win the next election.”
There is no fixed date for the next election, but it cannot be held later than January 2025. The next mayoral election will be held on May 2, 2024.
Mr Khan’s free school meal programme has been paid for using higher-than-expected collections of business rates and council tax.
The Government already provides free school meals on a universal basis for children up to and including Year 2.
After that point, the Government only provides lunches to children from households receiving certain benefits. For households on universal credit, they must earn less than £7,400 a year - after tax and not including benefits, and regardless of the number of children in the family - in order for their children to be eligible for the meals.
The lunches administered through the mayor’s scheme will therefore provide for children in Years 3-6.
It comes as polling from YouGov reveals that around a third (32 per cent) of parents and guardians of children in London between five and 11 years say they are ‘financially struggling’, including around one in six (16 per cent) going without basic needs or relying on debt to pay for them.