Teachers’ leaders have called on new Chancellor Nadhim Zahawi not to “interfere” over the issue of pay.

In a letter to the Cabinet minister, Patrick Roach, general secretary of the NASUWT teaching union, said it was “extremely disappointing” to hear his comments on Wednesday’s breakfast news, in which he promised that a 9% rise for early career teachers and a 5% rise for more experienced staff will go ahead.

Dr Roach said decisions relating to teachers’ pay are a matter for the review body process, involving consultation with trade unions, and that it is “entirely inappropriate” for Mr Zahawi to remark on the decision when the review body report has not been shared with the profession.

“It is … entirely inappropriate that, as Chancellor, you should seek to interfere in the process of consultation and negotiation which should follow the publication of the pay review body report, or for you arbitrarily to insist on capping the pay award at 9% for new teachers and 5% for experienced teachers,” Dr Roach wrote.

“Such interference can only do harm to industrial relations within the sector going forwards.”

Both the National Education Union and NASUWT have threatened strikes over pay in the autumn term.

Dr Roach said the Government needs to prioritise rewarding the teaching profession, adding that teachers have been “badly let down” and that a commitment to higher pay is needed to restore morale.

Speaking on BBC Breakfast on Wednesday morning, Mr Zahawi said he will honour a pledge he made as education secretary to raise teachers’ starting salaries by 9%.

“My submission to the pay review body was to say we need to get teachers’ starting salaries to £30,000, and that’s where the 9% pay rise… we will deliver on that this year and 7.7% next year, and of course for more senior teachers my submission to the pay review body was 5% over two years,” he said.

“We will look across Government, across departments at what the pay review bodies will recommend.”

He said he had submitted the plans for a pay raise for teachers when he was education secretary and that had been a manifesto pledge.

“We will deliver on that pledge, that is a promise I make teachers.”

Mr Zahawi was appointed to his new role following a wave of resignations, including by chancellor Rishi Sunak, over the Government’s handling of allegations of sexual harassment concerning ex-deputy chief whip Chris Pincher.

Headteachers’ leaders have expressed concern about the high turnover of education secretaries in the past few years.

Geoff Barton, general secretary of the Association of School and College Leaders, said: “While we extend a warm welcome to Michelle Donelan as Education Secretary and wish her well in her new role, we have to express our concern at the high turnover rate of education secretaries.”

He said Ms Donelan is the sixth person in the role in eight years, and the third during Boris Johnson’s premiership.

Mr Barton said: “Education is a vital public service and a complex sector which requires deep understanding, knowledge and continuity. This constant chopping and changing does not provide stable leadership.”

He said Mr Zahawi had introduced a White Paper with “very significant attainment targets and structural changes” to the schools system, while large sections of the accompanying Schools Bill had been withdrawn over concerns that it would mean too much centralised control over academies.

“Michelle Donelan will therefore face a considerable challenge in taking forward these proposals,” he said.

Mr Barton added that the “actual crisis” facing schools is the problem of teacher shortages after decades of falling pay.

“It is a crisis compounded by soaring energy costs which are putting intense strain on budgets that simply cannot withstand any more pressure,” he said. “These are real and present dangers to the education system that will require urgent resolution.”

Mr Barton said the pay award “must be fully funded by the Government so that schools are able to afford the additional costs”.

He said schools’ “budgets simply cannot withstand any further strain at a time when they are also being hit with soaring energy bills. This is what we expect from the Government and from the new Chancellor.”

Former children and families minister Will Quince resigned on Wednesday morning over the scandal in Westminster, and the resignation of schools minister Robin Walker followed soon afterwards.