Labour leader Sir Keir Starmer has criticised the government for being "asleep at the wheel" on the issue of reopening schools.
Speaking on Sky News, he argued that children could have been back in school by now if not for a "total lack of planning" by ministers.
Sir Keir added that, if it is possible to put up Nightingale hospitals, it is certainly feasible that the government can construct temporary classrooms.
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"There has been a total lack of planning," he said.
"From the day the schools were shut down, it was obvious what needed to happen to get them back open again.
"You needed a risk assessment, and you needed to look at the space. I've talked to loads of headteachers, and the points they have made to me were obvious and practical and could have been overcome."
He added: "If you could put up Nightingale hospitals – a good thing to do – you can certainly put up temporary classrooms, you can certainly take over libraries, community centres.
"Had there been work on this from the day the schools closed down, I genuinely think we could have had all our children back in school by now, but the government was asleep at the wheel, didn't get to this until too late in the day, and now we're in the situation where children will be able to do other things this weekend, but not be in school on Monday."