Conservative councils are opposing the government’s academisation plans, adding their voices to a growing number of rebelling local authorities.

Kent county council, the country’s largest Conservative-run education authority, unanimously voted last week to write to Nicky Morgan, the education secretary, to demand that she ditch her reforms.

Conservative-run West Sussex county council soon followed, and Paul Carter, a Tory councillor and chairman of the County Councils Network, said Morgan’s plans could lead to a “poorer education system”.

Schools Week revealed earlier this month that several councils and their leaders had publicly opposed the plans, including Birmingham, England’s largest authority, where councillors voted to reject several white paper policies.

Another raft of councils are now beginning to mobilise against the plans.

Roger Gough, Kent’s cabinet member for schools, said: “We work extremely well with academies across Kent.

“But the government appears to have come to a view that it knows what is better for schools than schools themselves. School autonomy is fine so long as it comes up with the right answer.”

Louise Goldsmith, leader of West Sussex council, has demanded Morgan rethink the “one-size-fits-all” academisation plans.

She said West Sussex debated the plans earlier this month: “Councillors of all political persuasions were united in their concerns about a lack of democratic accountability inherent within the proposals as they stand.

“Other concerns were raised about the council’s ability to fulfil current and residual statutory responsibilities, financial efficiency and the possibility of a very bureaucratic system being imposed.”

Warwickshire county council, where Conservatives hold the most seats, also voted to reject the plans.

Izzi Seccombe, the council leader, said: “We feel forced academisation takes choice away from parents and communities and removes local, democratic control. This places us, and all other local authorities, in an impossible position.”

Labour-run Luton borough council held an extraordinary meeting on Monday during which councillors voted to oppose the plans.

Other councils who have passed motions against the plans include Gateshead, Stockport and Rochdale.

Christine Blower, general secretary of the National Union of Teachers, has praised councils taking action.

“We applaud their determination to support local schools and champion the importance of a local, democratic and elected middle tier in education.

“The proposal to force schools into unaccountable multi-academy trusts has been rejected by parents, teachers, local authorities and MPs, including many Conservatives.”

The National Governors’ Association has also written to Morgan to raise concerns.

Its letter read: “There is considerable sadness from our members that their decisions will be overridden and their commitment, knowledge, values and skills are being ignored.”

A spokesperson for the Department for Education said: “We want to work constructively with the sector to deliver this and ensure standards continue to rise.”