Boris Johnson has repeated his pledge to increase school funding in his first House of Commons appearance since being appointed prime minister.

However, he failed to answer a call to say when schools will be given details of their funding settlement to enable them to start planning.

During his campaign for the Conservative Party leadership, Mr Johnson pledged an extra £4.6 billion for schools by 2022-23.

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During today’s appearance in front of MPs, Conservative MP Sir Geoffrey Clifton-Brown asked him to look at the distribution of funds between the highest and the lowest funded education authorities.

Mr Johnson replied: “That is of course what we are doing. That is the nature of the pledge and the undertaking we are making with the £4.6 billion that we have announced and the objective, as I think members will know by now is to lift per-pupil funding for primary schools to a minimum everywhere of £4,000 and a minimum everywhere of £5,000 for secondary school pupils.”

Jules White, of the WorthLess? headteachers’ funding campaign, told Tes that an immediate extra £4.6 billion would be “warmly welcomed”, and would broadly put schools back to where they were in 2010.  

But he added: “If, however, such a pledge comes with time constraints and there isn’t absolute certainty that we will not see any extra money taken away in parallel costs - such as wages, pensions and other levies - then it will count for much, much less.

“All school leaders want is straight, unvarnished commitments so that we can do our jobs properly. We will inform parents accurately and clearly about what Mr Johnson actually provides.”

He also called for funding for other public services that schools rely on.

He added: “£12 billion by 2023 is what we need. To coin a phrase: ‘No ifs and no buts’.”

Earlier, Labour leader Jeremy Corbyn asked the prime minister “when will he set out the detail of the exact funding settlement for our schools” so they can start planning.

Mr Johnson did not respond to this question, but had earlier told MPs he would start providing funding for frontline public services such as education “right away”.

On Tuesday, heads warned that the £4.6 billion figure was insufficient.

Geoff Barton, general secretary of the Association of School and College Leaders, said: “We hope he will immediately make good on his promise during the leadership campaign to reverse the education cuts. To achieve this objective he needs to invest an additional £12.6 billion by 2022-23, rather than the £4.6 billion he has pledged.”

He said the government should provide funding for the total cost of Monday’s teacher pay award “as a matter of urgency”.