Primary school governors told they can punish principals who refuse to fulfil 'professional and moral duty'

Headteachers have accused the schools secretary, Ed Balls, of urging council chiefs to threaten them with docked pay and written warnings if they go ahead with a boycott of tests for primary schoolchildren.

Heads said they were under mounting pressure to call off their boycott of the tests for 10- and 11-year-olds, due to start on 10 May, after school governors had been told they were within their rights to deduct pay and take disciplinary action against heads.

The Learning Trust, which is in charge of schools in Hackney, north-east London, has said governors could dock at least one day's pay from heads who joined the boycott. In a letter sent to governors of Hackney primary schools yesterday, the trust said: "Any refusal to make arrangements for the tests would be regarded as a breach of contract."

The trust had advised schools taking action that a notional amount of one day's pay can be deducted from staff salaries, a spokesman confirmed. Other London councils are thought to have sent similar letters.

Leeds Education, which runs the city's schools, has written to chairs of governors in primary schools, suggesting they "may wish to consider whether disciplinary action should be instigated" against a head who takes part in the boycott.

The Local Government Employers' organisation issued a statement advising governors to inform teachers who boycott the tests that "a breach has occurred and that the intention is to deduct pay". It added: "The higher the seniority or professional impact of the job, then the more right the employer has to insist that, where the inaction goes to the heart of the professionalism of the job and damages the employer's business, the employee is in breach of contract and all pay can be withheld." The organisation added that a "more measured approach" might be to withhold a proportion of pay.

The National Association of Head Teachers (NAHT), which is holding its annual conference in Liverpool this weekend, said the warnings to governors were the result of central government pressurising local authorities and amounted to an escalation in the dispute between heads and government. Balls has said heads have a "professional and moral duty" to conduct the tests, formerly known as Sats.

Mick Brookes, general secretary of the NAHT, said: "If [local authorities and government] want us to escalate this, we will. We are not going to stand idly by as our members are threatened.

"This is a legal dispute and we would not expect any disciplinary action to be taken against our members."

Balls has said if heads refuse to administer the tests, another "competent person" must be found who can – and the head could be told to stay away from school to ensure they do not prevent that person from doing the job.

But Stephen Watkins, headteacher of Mill Field primary school in Leeds, said: "If my governors were to ask me to not come in, I would still come in. I wouldn't allow other people to replace me.

"I would not allow them in without their passports and proof that they had been checked by the Criminal Records Bureau. By the time I had checked this, I would have got the children out of the back door."