In a speech on the weekend, Patrick Roach, deputy general secretary of NASUWT — which represents around 230,000 teachers in England and Wales — said that the new Education Act was a "crime against humanity, a smash and grab raid that will tear apart our communities," writes Graeme Paton at the Telegraph.
The legislation gained Royal Assent last week and now gives the Government increased powers to intervene and close down failing schools, paving the way for more academies and free schools to be created.
Coming just days after the union announced a wave of strikes in response to changes to pensions, a freeze on pay and job losses, Chris Keates, the NASUWT general secretary, later redistributed extracts from the speech via his Twitter account.
But a Coalition source said: "Language like this is very disappointing.
"The Education Act gives teachers greater powers over discipline in the classroom and protects them from malicious allegations from pupils.
"It is rather odd that a teaching union could be against measures that helps teachers raise standards on the frontline."
The legislation has led to the abolition of the General Teaching Council, and additional powers being brought "in house" by the Department for Education.
"We must not fall into traps that have been set for us. We need to reclaim progressive values within our schools and classrooms," Dr Roach said.
Dominic Raab, the Conservative MP for Esher and Walton and a former human rights lawyer, said:
"To describe legislation aimed at improving teaching standards in our schools as a crime against humanity is deeply offensive.
"It is insulting to trivialize the victims of such horrific abuse, and only shows how out of touch certain molly-coddled union bosses have become."
The act has given Michael Gove, the Education Secretary, the direct power to now order the closure of a state school without having to defer to a local authority, and as part of the legislature, when a failing state schools reopens as academies or free schools, they will be answerable directly to Whitehall, rather than their local authority.