Education secretary Nicky Morgan has launched an “extraordinary” attack as she draws up battle lines for the government’s attempt to justify removing the parental voice from academy takeovers.

Ms Morgan this week accused parents and campaigners who opposed the academisation of schools of using “underhand tactics” and “intimidating” parents.

She threw her support behind the big academy chains who, she said, have had their schools attacked, “scaring and intimidating” teachers and pro-academy parents.

Her comments come as the government launches a consultation on its education and adoption bill that proposes forcing “coasting” schools to become academies.

It also plans to remove the requirement to consult with parents and to compel governors to support the move.

However, the education secretary’s accusations have been met by disbelief from parents and teachers who have opposed their schools turning into academies.

A teacher involved in an antiacademy campaign said: “I have witnessed no intimidation of any sort of parents or teachers from the antiacademy activists, but rather an active campaign of suppression of our views by the governors and, in particular, the executive headteacher.”

She would only speak to Schools Week on the condition of anonymity because of fear of repercussions if she was seen to be raising concerns publicly.

Howard Stevenson, professor of educational leadership and policy studies at the University of Nottingham, said the Department for Education’s claims were a misrepresentation of reality.

“People, in their frustration, are having to do all sorts of things to open up the space for discussion – and they get compared to thugs. It’s extraordinary.”

Professor Stevenson, who is working on a study about the process of parental consultation during academy conversions, added: “It’s the people opposed to academisation who have felt intimidated – teachers fear for their jobs if they express dissent.”

But Ms Morgan said: “For too long campaigners have deployed underhand tactics, spread malicious rumours and intimidated parents in order to deny children the opportunity of success.”

The claims were backed by academy chain bosses, including Dame Rachel de Souza from the Inspiration Trust and Sir Dan Moynihan, chief executive of the Harris Federation.

Their comments were sent in a press release to journalists titled “headteachers hit back at enemies of academies”.

However, a different press release to launch the consultation appeared on the government’s website, which campaigners say was “toned down” with some of the accusations about parents left out.

Kevin Courtney, deputy general secretary of the National Union of Teachers, said the Department for Education (DfE) had “plumbed new depths”.

“The unsubstantiated attacks by the DfE on parents and local communities whose only crime has been to defend their school against the government’s strong-arm tactics to force schools into academy status, including deploying bullying academy brokers, is utterly shameful.”

The DfE press release also said campaigners had “refused to provide important information” during takeovers, but did not say what that information was.

In 2013, the department was criticised by the Information Commissioner when it refused to release free school information to the British Humanist Association.

During a legal tribunal, the department used a survey by the New Schools Network charity to claim that free school supporters were being intimidated – but the judge said its reliability was poor and it “fatally undermined” the case. He ordered the information’s release.

New Schools Network has now been dragged into the row after it was accused of acting as a “battering ram” for the government’s policies by Russell Hobby, general secretary for the National Association of Head Teachers.

It followed the charity’s latest press release attacking Ofsted and calling for more accountability for schools, as under the free school and academy models.

The charity said the release applied to both maintained schools and academies. The government’s new consultation seeks views on proposed definitions for coasting mainstream schools, special schools and pupil referral units. It will run until December 18.