The government is under growing pressure to explain why it has waited until days before the start of the autumn term to order the closure of schools found to contain a lightweight form of concrete that can collapse without warning.

The Department of Education (DfE) yesterday told more than 100 school buildings to close following years of warnings from experts about reinforced autoclaved aerated concrete (RAAC).

The lightweight material was used across the UK and in many types of buildings, including hospitals, from the 1950s to the 1990s but has now passed its 30-year design life.

The DfE said yesterday that “new evidence” had emerged over the summer which required buildings that contain RAAC to close immediately.

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