A survey by the Local Government Management Board shows that about one in 12 headteacher and deputy head posts are vacant or being filled by stand-ins. But the board says there is no shortage of volunteers wanting to take on the head's role temporarily while a permanent replacement is found.
It dismisses research by the National Association of Head Teachers published earlier this year showing increases of up to 29 per cent in headteacher vacancies and rejects claims by the union that teachers are being forced to act up as heads to conceal a shortage.
The survey, answered by 110 local authorities, found there were 2,807 temporary appointments for heads and deputies, this would equate to about 4,000 for all English and Welsh education authorities making 8 per cent of the total. More than one in 10 primary deputy headships were either vacant or being temporarily filled.
This year's figures are thought to have been inflated by an exodus of senior staff because of rule changes that will make it harder to retire early in future. According to the DFEE, in the first nine months of this year 21, 300 teachers left the profession, of whom 3,600 took early retirement. Pounds 2,600 were heads and 1,800 deputy heads.
Both sides hope the School Teachers' Pay Review Body, currently deciding next year's pay settlement, will listen to their argument. The heads are demanding extra pay to attract recruits to senior posts, while the management board sees no case for added incentives.
Graham Lane, leader of the management side, said: "The NAHT's figures are not borne out by reality.
"There is no shortage of headteachers. What we need to do is not offer extra large pay rises to attract candidates for headships but to remove some of the administrative burdens they face.
"I would advise the Government and the pay review body to believe the figures given to them by the employers, and not rely on the head teachers' union for information."
But the NAHT dismissed the board's claims and said the survey confirmed its own findings.
Kerry George, the union's senior assistant secretary for pay and conditions, said the board's claims were "nonsense".
"We are absolutely satisfied that our findings are accurate. We are concerned that the authorities should be seeking to make light of what is accepted by most people as a crisis. We are also concerned by the things we are hearing from our members about local authorities trying to conceal the crisis. In some authorities deputies have been told they are obliged to fill a head's post and pressurised into acting up."
The management board's survey found there were 964 vacancies or posts filled on a temporary basis for headteachers in primary schools,123 in secondaries and 99 in special schools. For deputy heads the figures were 1,279 for primaries, 243 for secondaries and 99 for special schools.
The NAHT's research was based on advertisements for vacancies. It showed a total of 2,516 vacancies were advertised for primary headships in the year from September 1996, up 29 per cent on the previous 12 months. In secondaries there were 449 vacancies, an increase of 24 per cent. It is therefore difficult to make direct comparisons with the LGMB survey.
Evidence from the headteachers' unions to the pay review body this year argues for higher pay for heads and deputies, compared with classroom teachers, to help resolve recruitment problems. The NAHT says comparisons with industry suggest this should mean rises of around 10 per cent.