Further strikes are likely over plans to curb public pensions

More rises in payments are expected over the following two years so the Treasury can cut the bill by £2.8bn a year

Trade Union leaders warned that an "autumn of discontent" had come a step nearer yesterday after the Government refused to water down plans to curb public-sector pensions.

Ministers outlined plans to raise pension contributions by an average 3.2 per cent for 2.5 million teachers, civil servants and NHS workers from next April, insisting the £1bn of savings they would bring had already been pencilled in by the previous government.

Detailed talks on the proposals will take place over the next month before ministers and TUC leaders resume their negotiations in September. Unless the Government softens its stance then, a series of co-ordinated strikes looks likely. Brendan Barber, the general secretary of the TUC, said: "Only if the Government demonstrates real flexibility in the coming talks and shows that it is genuinely listening and prepared to change course, will it avoid more unions... planning industrial action later this year."

He warned that millions of public-sector workers, already in the middle of a wage freeze and facing a huge squeeze on their living standards, would be forced to pay significantly more into their pensions. Ministers argued that yesterday's figures should come as no surprise and did not alter the prospects of reaching agreement with the unions. They pointed out that no one earning under £15,000 a year would face higher pension contributions.

Danny Alexander, the Liberal Democrat Chief Secretary to the Treasury, said the proposals were the latest step towards putting public-service pensions on a sustainable path. "We are ensuring that those with the broadest shoulders will bear the greatest burden. The lowest paid will be protected, and the highest paid will face the biggest increases," he said.

Further rises in payments are expected over the following two years to enable the Treasury to cut the public-sector pensions bill by £2.8bn a year. Detailed proposals for local government, the fire and police services will be published shortly. Firefighters became the latest group of workers to warn that industrial action is on the cards. The Fire Brigades Union, which is consulting its members, said there was growing support for action and a ballot on a nationwide strike is likely soon.

Teachers and heads warned that schools could be disrupted again by strike action this autumn. The National Association of Schoolmasters Union of Women Teachers, the only one of the big three teaching unions not to walk out on a one-day strike last month, said it was committed to industrial action to protect pensions.

Chris Keates, its general secretary, said: "It is grossly unjust that teachers and other public-service workers, who are already facing an imposed pay freeze, [are] being faced with paying what is in effect an additional tax for a financial crisis they did not create."

Under the Government's plans, a headteacher earning £100,000 a year would have to pay an extra £2,000 in contributions next year. The blow would be softened for lower-paid teachers – those starting on £21,000 a year would only pay an extra £128 a year.