The survey showed that they spent almost half their time on administration. A fifth of this work would be more appropriately carried out by someone
In larger schools where the head is the only teacher without a class commitment, he or she invariably takes on jobs when there is no one else available to deal with them.
The National Primary Headteachers Association commented: "We end up with the highest paid professional in the school undertaking low-value administrative tasks."
It added: "As with so many other aspects of the current education system, this is not a situation that would be tolerated by secondary headteachers."
The NPHA, which is involved in the research, is urging the Government to fund a full-time assistant in every school.
It wants ministers to consult the General Teaching Council on a sliding scale of support for schools based on the number of pupils on roll.
The association said there was an obvious and urgent need for heads to delegate more
But the question on the lips of heads, who took part in the research projct carried out by Queen's University, Belfast, with funding from the Centre for British Teachers, was: "To whom?"
The NPHA said most primaries did not have full-time administrative support and the smaller the school the less likely there was to be a designated deputy head.
Alongside the admin support, the association wants the GTC to establish defined levels of non-teaching monitoring and support time for teachers.
It urged ministers to consult on the optimum class size for pupils of all ages and added its voice to the growing call for a national funding formula for schools.
Earlier this month Chris Woodhead, the chief inspector, said it was "unacceptable" that some primaries received more than pound;2,500 per pupil, while others had to make do with pound;1,300.
Other supporters of a national funding formula are the two headteacher unions, the Liberal Democrats and the School Teachers' Review Body.
The NPHA called on the Government to establish a guaranteed funding entitlement for all children, irrespective of age, race, gender or where they happen to live.
"The present system is patently failing to provide a level playing field for pupils across the country," the association said.