Rishi Sunak refused to properly fund a school rebuilding programme when he was chancellor, despite officials presenting evidence that there was “a critical risk to life” from crumbling concrete panels, the Department for Education’s former head civil servant has said.

After the department told Sunak’s Treasury that there was a need to rebuild 300 to 400 schools a year in England, he gave funding for only 100, which was then halved to 50, said Jonathan Slater, the permanent secretary of the department from 2016 to 2020.

Conservative ministers more widely believed a greater funding priority was to build new free schools, Slater told BBC Radio 4’s Today programme on Monday, as pupils returned to many schools in England for the new term.

“For me as an official, it seemed that should have been second to safety,” Slater said. “But politics is about choices. And that was a choice they made.”