Research by the National Association of Head Teachers (NAHT) suggests that at the end of 1999-2000, there were 640 advertised vacancies, compared with 334 in the previous year.
The union said schools in London were particularly badly affected, with 75% of primary schools reporting fewer than 10 applications per post.
Positions remained unfilled because applicants were often not considered good enough, the NAHT said.
Pay increase
General secretary of the NAHT, David Hart said the situation was stark.
"School leadership posts are not attracting nearly enough quality candidates - workload, bureaucracy and high stress levels are discouraging senior staff from applying," Mr Hart said.
"Salaries paid to heads and deputies are inadequate - nothing less than a significant across-the-board pay increase will arrest a decline which has serious implications for the government's drive to raise standards in schools."
'Turning the corner'
School Standards Minister Estelle Morris dismissed the research saying the NAHT was simply seeking a pay rise for heads.
Recruitment figures released on Thursday would show a "big upsurge of applications from teachers wanting to become heads", she claimed.
They could now earn up to £76,000 compared with £57,000 in 1997, she added.
"As with teacher recruitment, where we are now clearly turning the corner, the evidence is that we are doing the same with headship training.
"The facts should not be lost in various unions' annual bids to attract the attention of the pay review body," she said.
'Paperwork and bureaucracy'
The Conservative party said the statistics were "appalling", and showed a crisis in schools.
"David Blunkett is determined to drown head teachers under a tide of paperwork and bureaucracy," shadow education secretary Theresa May said.
"As a result, more and more are complaining of stress and work overload leading to many deciding to give up teaching as a career."