Two of the biggest education unions have jointly called on the prime minister to “keep his promise” on education in the upcoming spending review.

Teachers’ leader Mary Bousted described the decision on how much funding to award schools as a “moment of truth for the government”, while heads’ leader Paul Whiteman called for a “radically more ambitious package of investment” from the Treasury to combat the learning lost during the pandemic.

In their joint submission to the 2021 comprehensive spending review, the NEU teaching union and NAHT school leaders’ union said Boris Johnson’s “fine words” on education recovery “must now be backed up with concrete proposals and adequate funding”.

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They argued that the rejection of the £15 billion Covid catch-up plan proposed by the former education recovery commissioner Sir Kevan Collins was a “very disappointing start”, and that the government must now tackle its “legacy of broader education underfunding”.

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In order to restore funds to 2015 levels, the unions said that, in 2021-22, an additional £7.3 billion in revenue funding and £2.8 billion in capital funding would be needed per year for those ages 2 to 19.

But Mr Whiteman, general secretary of the NAHT, argued that the government must go further than this.

“Schools need a radically more ambitious package of investment from the Treasury in order to get the job done,” he said.

“But investment is about more than ‘recovery’. There must be more ambition for our young people than simply restoring budgets to 2015 levels. This and subsequent generations of pupils deserve better.

“The government must see education as an investment in this country’s future, not a drain on the nation’s finances. The education secretary must seize the opportunity of the comprehensive spending review and convince the chancellor and the prime minister to turn rhetoric into investment.”

And Dr Bousted, joint general secretary of the NEU, said this was a “moment of truth” for the government.

“It can either continue the improvement in education funding started by the 2019 spending round or return to the long days of 2010s’ austerity,” she said.

“The government ultimately must decide what type of country it wishes us to be - a low-wage, low-skill, low-investment economy or a high-investment, high-skill, high-productivity economy, leading to high wages for its citizens.

“Our children deserve a decent future after the chaos of the past 18 months.”

A government spokesperson said: “There is a shared commitment across government to support children whose education has been affected by the pandemic.

That is why we have committed to an ambitious, long-term education recovery plan, investing over £3 billion and significantly expanding our tutoring programme to support children and young people to make up for learning lost during the pandemic.

“We do not comment on speculation in the run up to fiscal events.”