An analysis of adverts placed in The TES has revealed an increase of almost 40 per cent on the same period last year.
Well-known schools such as Holland Park comprehensive in west London, where Tony Benn sent his children, are now having to re-advertise. The headship was once described as the most highly-paid post in teaching.
David Hart, general secretary of the National Association of Head Teachers, said: "(The) headship recruitment (situation) is very bleak. It is a lesson the Government has to learn very quickly."
The demand for heads this year had been expected to mirror that for 1999. The unexpected rise in the number of vacancies has been put down to escalating bureaucracy driving heads out, and a reluctance by some to go through the trauma of performance pay and threshold assessments.
The problem is not limited to London. John Howson, an independent recruitment analyst, said small rural schools were being hit particularly hard.
He said "In those schools, the head is closer to the staff and having to decide whether they will get through the threshold - and get the pound;2,000 - or not."
Recruitment difficulties are not confined to the top jobs. Last week six local authorities placed block adverts seking newly-qualified primary teachers - very unusual in the past few years.
Several schools are still seeking large numbers of staff and may well find it difficult to recruit enough qualified staff for the start of the new academic year.
These include Barr's Hill in Coventry, advertising five posts; St John Almond RC high in Liverpool, with seven vacancies and Ducie high in Manchester, with six. Robin Brabban, head of Barr's Hill, said jobs in industry were now often more attractive to trained maths, French, technology and science teachers.
Durham head Tim Gunn will leave Wolsingham primary school after 30 years as a teacher this month to become a lorry driver, delivering food for a supermarket chain. Tim, 51, said he had wanted to be a trucker as a child, and despite following an academic path, had driven buses in his holidays to cover his mortgage. Now, fed up with the growing pressures on teachers, he has deicded to seek a new challenge.
He said: "Every head will tell you there's too many administrative procedures. The Government has set targets for the local education authorities, who then set targets for schools and there is a tremendous amount of pressure.
"If you made a list of all the things a head was required by law to do there would not be enough time in the day to do them."