Of 6,468 teachers who had retired by the end of August, 1,700 went on reduced benefits, 1,755 prematurely retired on full pension and 2,622 retired normally. Nearly half (786) of those quitting early were doing so at the earliest opportunity, aged 55 or 56. Classroom unions say the figures reflect the Government’s failure to retain older staff.

Sue Johnson, head of pensions at the Association of Teachers and Lecturers, said when ill health retirements hit 26 per cent, the Government took action to stem the flow, mainly by making it more expensive for local education authorities to let staff go early.

She also fears that teachers may face poverty later in retirement, when they become too old to top up their reduced benefits by part-time, supply or alternative employment.

A Department for Education and Skills spokeswoman said: “Although there is a reduction in the amount paid, the pension is paid for a longer period so the financial effect on the individual (assuming an average life expectancy) is neutral.”

A teacher aged 55 and six months at retirement, with 25 years’ service and an average final-year salary of pound;30,000, would lose pound;2,212 from their annual pension, and pound;4,022 from their lump sum. They would get pound;7,162.50 a year instead of pound;9,375, and a pound;24,103 lump sum instead of pound;28,125.