After an interview with ITV News in Westminster, the cabinet minister criticised others for being "sat on their arses" and claimed the government had gone "over and above" in addressing concerns relating to reinforced autoclaved aerated concrete (RAAC).

While her mic was still on she said: "Does anyone ever say 'You know you've done a f***ing good job because everyone else has sat on their arses and done nothing.

"No signs of that, no?"

Read more: All the schools affected by concrete crisis

Ms Keegan later apologised and admitted she was "frustrated with the interviewer" who was "making out it was all my fault".

Thousands of pupils face disruption at the start of term this week following an order to fully or partially close 104 schools because of concerns about RAAC, which is prone to collapse.

Pupils face being taught in temporary classrooms, on different sites or even forced into pandemic-style remote lessons.

Critics have accused the Tories of a "shambolic" handling of the situation, saying risks associated with the dangerous material have been known about for years.

Ms Keegan is due to be interviewed on the Politics Hub with Sophy Ridge on Sky News tonight at 7.30pm.

Asked repeatedly who she meant had been "sat on their arses", Ms Keegan insisted it was "nobody in particular".

She said: "It was an off-the-cuff remark, after the news interview had finished. I’d like to apologise for my choice language, that was unnecessary."

Pressed on who she was frustrated with, Ms Keegan said: "Actually, it was the interviewer, because the interviewer was making out it was all my fault and that’s what I was saying, do you ever go into these interviews where anyone ever says anything but you’ve just done a terrible job?"

She said it is "frustrating" because she and her team have been working hard to deal with the issue of unsafe concrete, and she hasn't slept due to "worrying about this".

She also indicated she was frustrated with those who have not responded to questionnaires asking about whether schools have the dangerous aerated concrete present.

Speaking to Sky News, Cas Evans, headteacher at Parks Primary, said: "That's our education secretary using that language for the situation?

"What I would like to say is please Gillian, come and see my school, come and really understand what RAAC looks like, what RAAC is in a school, what happens when you close a school… but just come and see what your serving headteachers are doing in order to maintain a good education.

"I am horrified by that clip, and I think that something needs to happen for somebody to say that because I worked from the moment we got the notice of closure. I worked every weekend, late into the night in order to make things work.

Ms Evans added her staff have also worked hard since having the closure notice, and said: "Nobody is sat on their backside."

In a statement in the House of Commons this afternoon, Ms Keegan promised to publish the full list of affected schools "this week" as she sought to stress that disruption would be minimal.

Addressing MPs, she said: "Absolutely nothing is more important than the safety of children or staff" but that the "vast majority of schools are unaffected".

Ms Keegan added that schools with suspected dangerous concrete will be surveyed in "a matter of weeks" and "in many cases, a few days".

In response, Labour's shadow education secretary Bridget Phillipson accused Ms Keegan of presiding over an "utter shambles".

"The mark and measure of each of us as politicians is our willingness to take and to accept responsibility," she said.

"Collective responsibility, not just for our own actions, but those of the governments in which we serve. And this week, as the school year begins, there is an awful lot of responsibility for ministers to take for what is an utter shambles."

She added: "The defining image of 13 years of Conservative government - children under steel props to stop the ceiling falling in on their heads."

Keegan 'living on another planet'

Downing Street said it was right that Ms Keegan had apologised.

The prime minister's official spokesman said: "I think that the language used obviously is not acceptable. It is right that the education secretary has apologised for that.

"But at the front of parents' minds will be the situation in their schools and I think that is what they will want to hear more about."

But Labour leader Sir Keir Starmer said it was a "farce" to see a Tory minister "blame anyone but themselves".

He said: "I think this whole situation is descending into farce.

"The government has dropped the ball here, failed to prepare.

"The prime minister bears responsibility for some of the key decisions along the way.

"And instead of coming out today and saying, 'This is what we're going to do to fix the problem, which we have made a lot worse', you've got members of the cabinet coming out trying to blame other people, trying to blame people within their own teams and to say, essentially, 'put responsibility anywhere but on the government'."

Meanwhile Liberal Democrat education spokeswoman Munira Wilson said: "Gillian Keegan's disgraceful comments add insult to injury for parents who've seen their children's return to school ruined by this concrete crisis.

"Expecting people to thank her when children are being taught in classrooms at risk of collapse shows Keegan must be living on another planet."

Questions remain over the extent of the RAAC emergency, the timing of the government's announcement and how the repairs will be funded.

Earlier, Mr Sunak acknowledged hundreds more schools in England could be caught up in the crisis as he faced accusations he failed to fund a programme to replace ageing classrooms while chancellor.

The prime minister said that 95% of England's schools were unaffected, leaving open the possibility that more than a thousand could be impacted.

RAAC is essentially a lighter-weight form of concrete, used to build roofs, schools, colleges and other buildings from the 1950s until the mid-1990s.

The government said "new information" about RAAC came to light over the summer, prompting them to issue the safety warning just days before the start of the school term.

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RAAC: The once wonder material causing a chaotic start to the academic year

But experts have long-warned the material has now reached the end of its shelf life and is liable to collapse.

Jonathan Slater, who was permanent secretary at the Department for Education (DfE) from May 2016 to August 2020, claimed the Treasury had failed to fully fund school rebuilding schemes despite the government knowing there was a "critical risk to life".

Mr Sunak dismissed that criticism as "completely and utterly wrong".

But Labour insisted he "bears huge culpability for his role in this debacle" - saying funding for rebuilding schools has been slashed over the years.

Analysis published by the party found that spending on school rebuilding between 2019 and 2020 was at £765m, but this fell to £560m the following year.