It has emerged that the Government will not need a new Act of Parliament to raise teachers' pension age from 60 to 65.
The Treasury says the change can be brought in through the existing 1972 Superannuation Act. A spokesman said that there would be an opportunity for MPs to debate the issue.
But teaching unions say that, without a separate parliamentary Bill to introduce the change, there was no guarantee that this would happen.
Sue Johnson, the Association of Teachers and Lecturers' head of pensions, said: "This Government does lots of things through regulations which means they slip through without debate. They are laid before Parliament but there is no debate on them unless someone specifically calls for it. We will be lobbying MPs and I very much hope they will realise the importance of the issue."
The plan, announced in a Department of Work and Pensions paper last month, has caused uproar among teachers, with unions warning that members will opt for career changes in their 30s and 40s rather than face the prospect of working until they are 65.
Brian Clegg, pensions expert at the National Association of Schoolmasters Union of Women Teachers, said some had panicked and were planning to leave teaching and draw their pensions early.
He urged them not to, saying that if they did decide to leave the profession, they should defer their pension so that they could claim it at its full value.
The Department for Education and Skills says it will conduct a detailed review of the teachers' pension scheme and consult unions and employers before proceeding with the change, expected by 2006.
The change will apply to all public-sector workers including teaching assistants and local education authority officers who are covered by the local government pension scheme, which has already begun its review.