Those promoted to an assistant headship could find the difference to their pay, compared with that of a classroom teacher, is as little as pound;1,000 even less if the teacher has a teaching and learning responsibility payment.

This has led to fears for the future of headteacher recruitment, as there is no incentive for teachers to climb to the first rung of the leadership ladder.

This week’s figures also confirm a significant overlap in salaries, with half of primary heads, three- quarters of deputies and half of assistant heads earning between pound;40,000 and pound;50,000. This makes primary headships, in particular, no longer very attractive, especially with the huge accountability that comes with the role.

As the National Association of Head Teachers points out, it can be more lucrative and less stressful to be the deputy of a large school than to become the head of a slightly smaller one.

Typical pay for a deputy or assistant headships ranged from pound;39,000 outside the London area to pound;57,000 for those in inner- London secondaries.

Magnus Gorham, assistant secretary for salaries, pensions and conditions at the NAHT, said: “Something has to be done about the pay of assistant heads. There is no financial incentive for people to take on the role, so only the most ambitious are going to take it on.

“This poses big questions for the recruitment crisis in primaries, as people will not want to join the leadership group on this rung.”

Despite these concerns, the survey shows that many teachers in the leadership group were able to make progress up the pay scale.

Between last academic year and 20056, around half of senior staff moved one point up the scale and around 15 per cent moved up more than one level.

For classroom teachers, pay increases were all but certain throughout the first five years of teaching, and 95 per cent of those who then applied to the upper pay scale were successful.

Once on the first rung of the upper scale, however, only 40 per cent had progressed after a year.