Teachers have claimed that the education secretary is using "clumsy" tactics to distract from his "lamentable performance" after he reportedly accused unions of forming an "unholy alliance" with the opposition to block school reopenings.
Reports suggest that Gavin Williamson joked that the NEU teaching union was the "no education union" during a meeting with Tory backbenchers.
He also claimed the unions had been working with the Labour Party to keep children out of school, and said all education authorities had reached a stage where they could press on with reopenings, according to The Times.
Mary Bousted, joint general secretary of the NEU, said the comments – reportedly made during a meeting of the 1922 Committee – were a "clumsy attempt" by Mr Williamson "to divert attention from his own lamentable performance as education secretary – and his failure to work with the profession to achieve the safe opening of schools".
She added that the NEU's actions were "hardly obstructive".
"The NEU has consistently said that we want to see as safe a wider reopening of schools as possible and again, if possible, a full return in September," Dr Bousted said.
Coronavirus: 'Piecemeal information' on reopening schools
"What we have asked for is sight of plans for wider reopening and the scientific evidence that backs them. This is hardly obstructive.
"Headteachers are crying out for clear guidance for September and do not want a repeat of the piecemeal information they have been provided with so far.
"We are presuming the government will have the foresight to also include in its guidance for what to do in the occurrence of a second spike nationally or regionally."
The Association of School and College Leaders did not wish to comment on the reports.
School leaders' union the NAHT and the NASUWT teachers' union have been approached for comment.
A Department for Education spokesperson said: “We are working to get all pupils back in the classroom in September.
“Last week, secondary schools began welcoming back Year 10 and Year 12 pupils and primary schools now have the flexibility to invite more children back if they have capacity, as part of our phased plans, which are guided by the latest scientific advice.
“We will shortly be publishing further details to help schools prepare for September.”