Around 700,000 children in England are attending schools that need major repairs after years of underfunding, the National Audit Office (NAO) said.

The head of the public spending watchdog said that, despite assessing the possibility of building collapse or failure causing death or injury as "critical and very likely" in 2021, the Department for Education (DfE) "has not been able to reduce this risk".

Around 24,000 school buildings - more than a third of the total number in England - are beyond their estimated design lifespan.

School leaders have accused the government of dangerous neglect, describing the scale of building safety issues as "shocking".

A major cause of concern is the prevalence of reinforced autoclaved aerated concrete (RAAC), which is prone to failure and was regularly used between the 1950s and mid-1990s.

The DfE has been aware of the potential risk posed by RAAC since 2018 after a roof collapsed at a Kent school.

But the extent of potential problems in other schools remains unknown.

The NAO said the focus is now on 14,900 schools built during the period when RAAC was used in construction.

Of these, 42% have confirmed they have undertaken work to identify the concrete - but potential risks are yet to be identified in the remaining schools.

By May this year, 572 schools had been confirmed as potentially containing RAAC and the DfE is working with them to mitigate the safety of staff and pupils, the report said.

'Shocking' scale of safety issues

In its submission ahead of the 2020 Spending Review, the department said it needed £5.3bn a year of capital funding to maintain schools and mitigate the most serious risks of building failure.

Due to the time it would take the DfE to expand its school rebuilding programme, it requested an average of £4bn a year between 2021 and 2025.

The Treasury subsequently allocated an average of £3.1bn, leading education bodies to use limited funding on the most urgent problems, at the expense of general remedial work to prevent building failure in the future, the report said.

NAO head Gareth Davies said that the department must effectively target its resources.

Julie McCulloch, director of policy at the Association of School and College Leaders, said: "It is perfectly clear that the government has made a conscious decision to deprioritise education over the past 14 years and the deterioration of the school estate is one of the results of this mindset."

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Paul Whiteman, general secretary of the National Association of Head Teachers, said safety in schools should be "a given".

He added: "These shocking figures lay bare how far short the government is falling in its efforts to ensure school buildings are safe and fit for purpose for children and staff."

Labour MP Dame Meg Hillier, chairwoman of the Public Accounts Committee, said: "After years of firefighting issues, parents need reassurance that the department knows where, when and how any risks to their children will be remedied."

A DfE spokesperson pointed to the School Rebuilding Programme and its allocation of £15bn towards "keeping schools safe and operational" since 2015.

"Nothing is more important than the safety of pupils and teachers which is why we have been significantly investing in transforming schools up and down the country," the spokesperson said.