Paul Whiteman, general secretary at school leaders’ union NAHT, said: “This is nothing short of an overtly hostile act from the government and an attack on the basic democratic freedoms of school leaders and teachers.

“At a time when the government should be building bridges with the profession, the timing of this couldn’t be worse. Not only are the government’s proposals for minimum service levels fundamentally undemocratic, they are utterly unworkable in a school setting. There are a range of very basic questions that the government seem to have not even considered, let alone are able to begin to answer.

“The contempt that this government has shown for workers and their representatives is astounding. Unions were told about this news after the press had already been briefed. The government says it wants to enter talks with unions about this but sees attention grabbing headlines as more important than constructive dialogue. When it comes to industrial relations, this government simply doesn’t seem to know what it’s doing.”