Now the Houses of Parliament are being tested for crumbling concrete as the crisis grows

Parliament is being tested for a form of crushed concrete that has already caused the closure of more than 100 schools.

Surveyors are on the parliamentary estate looking for reinforced autoclaved aerated concrete (Raac), which is a lightweight building material used from the 1950s to the mid-1990s, but is now believed to be at risk of collapse.

The presence of the material in schools has sparked an escalating crisis for Prime Minister Rishi Sunak after last week's announcement that 104 of them would have to be closed. Some theaters announced on Tuesday that they would be closing, and the National Theater said it had found Raats in some of its backstage areas.

said a source Bloomberg, who first reported the story, that tests were still ongoing but were unable to say if Raac had yet been located.

If Raac is found, it will add to the significant problems at the troubled parliamentary estate, which urgently needs basic repairs such as asbestos removal, fire risk reduction, plumbing renewal and maintenance of the building itself.

It is estimated that any work on the Grade I listed building could take between 46 and 76 years and cost between £11-22 billion if carried out during the parliamentary recess.

In other developments today, unrepentant Education Secretary Gillian Keegan told headteachers who have not responded to an inquiry into crushed concrete to “get off their backs” and tell the Government if they are affected.

Keegan said she hoped all the “publicity” surrounding Raac in the buildings would force school authorities to complete a government questionnaire on the matter by the end of this week. Ms Keegan has been criticized for placing the blame on schools during this crisis, with one union leader describing the comments as “outrageous”.

She lashed out at those who “sat on their asses and did nothing” in a swearing-in on Monday, saying 5% of schools, or the bodies responsible for them, had yet to respond to a questionnaire sent by the Department for Education . DfE) about Raac on their websites.

He told Jeremy Vine on BBC Radio 2 on Tuesday: “Now I'm hoping all this publicity will get them off their backs. But what I would like them to do is respond because I want to be the Secretary of State who knows exactly in every school where Raats is and takes action.”

Principals are scrambling to find temporary classrooms ahead of the new academic year, while others have been forced to replace face-to-face classes with distance learning.

Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), said: “This is the second display of displeasure by the Education Secretary in a row – albeit without the swearing attached this time – and it's not very helpful.

“Schools are expected to identify Raac, even though it is a specialist area and they are unlikely to have staff who are experienced in this area.

“They have received little help from the Department of Education, who will know which schools have not returned inquiries for several months and who have had plenty of time to contact them. The education secretary would do better to provide support, rather than blame.”