Ministers are under pressure to spell out their plans to make schools safe from aerated concrete as pupils return to school for the first day of a new term today.

Gillian Keegan, The Education Secretary, confirmed on Monday There are 104 schools previously classed as non-critical now have emergency procedures in place following fears over crumbling concrete.

Forty-one hospitals and at least six courts are also known to be affected by RAAC, the crumbling type of concrete that was widely used in the second half of the 20th century. 

But experts warn this could be an underestimate and the material is likely widespread throughout the public sector, with private businesses also likely plagued.

Politicians are facing difficult questions about how some buildings that still form part of the nation’s vital infrastructure were erected in the 1960s with roofs designed to last just 30 years.