Twelve unions, including the major teaching organisations, staged the protest after concessions failed to placate them over proposals to raise the normal retirement age from 60 to 65.

They argue the move will discourage people from becoming teachers and prompt burnt-out professionals to quit. The Association of Teachers and Lecturers said the pensions change is the biggest issue now facing its 160,000 members.

Figures from last year reveal that 38 per cent of teachers who retired left before the age of 60, not counting those who left early because of ill-health.

Changing the retirement age midway through the careers of thousands of teachers will undermine confidence in the pension scheme and demoralise staff, the unions said.

Mary Bousted, ATL general secretary, said some of the proposed changes to the pension system were long overdue. But she said any benefits were outweighed by forcing teachers to work until the age of 65, which was “Victorianisation, not modernisation”.

She said: “Raising the retirement age will mean teachers who have given loyal service to generations of children and young people being forced to remain in posts which require energy and stamina, who are simply used up.”

She said that the extra costs of pensions changes could lead to some teachers opting out of the scheme altogether.

Teachers will be expected to contribute more to pensions than the current 6 per cent of salary under plans outlined in a Department for Education and Skills consultation paper. In return, the Government is offering new benefits, including equal rights for unmarried partners and paying spouses’

pensions for life. Payments would also be boosted by basing them on a 60th rather than an 80th of salary per year of service, But teachers will have to pay extra for these benefits - between pound;100 and pound;660 a year - and unions say they cannot afford it.

Changes to ill-health retirement are also controversial. In future, teachers could have benefits cut if they are too ill to teach, but can still do another job.

Steve Sinnott, general secretary of the National Union of Teachers, said:

“These proposals would damage the recruitment and retention of teachers at a time of persistent shortages.

“Teaching is such an intensive activity, it’s more difficult for them to work beyond 60. Our members were always led to believe they could retire at 60. They’re very angry: there’s a big difference between choosing to work to 65 and being forced to.”