The leader of the TUC has dismissed plans to raise the public sector retirement age to 65 as a "quack remedy" for the pensions crisis.
Mr Barber attacked a 'work-till-you-drop' culture
Brendan Barber said this would mean a "work-till-you-drop" culture and called for unions to act for "justice".
Unison leader Dave Prentis reiterated threats of strikes to defend pensions.
But Tony Blair's pensions chief, Adair Turner, told the TUC Congress in Brighton there were no "easy answers" to a multi-billion pound shortfall.
Mr Turner, whose Pensions Commission is due to report on the issue in November, said he was "aware" of the figures and would allow himself the "best shot" at addressing the problem.
The state system would have to become more means-tested or either the retirement age or taxes would have to go up.
Mr Turner said people were living longer and there was "nobody clever enough" to create a pensions system to cope with that "which doesn't involve one of those three things or some mix".
One Unison delegate said a later retirement age for "the lower paid in our society" meant those who "do not live longer" would still end up "having to work longer".
Mr Barber said: "Public servants have been given a pension promise and they expect that promise to be kept."
He added: "Let's step up our campaign for pensions justice."
Last October an interim report from the Pensions Commission suggested a mixture of higher taxes, more saving and an increased average retirement age was needed to solve the pension crisis.
Mr Turner believes many people on low incomes have been put off saving because they fear it will eventually bar them from receiving means-tested benefits such as the Pension Credit.
To cheers, Mr Prentis told the TUC Congress: "We will take strike action to defend our pensions. We will fight proposals to raise the pension age."
He accused MPs and "fat cat" company directors of "double standards" in awarding themselves higher pensions.
Mr Adair has argued that 12 million people in the UK are not saving enough for their old age.
Trade and Industry Secretary Alan Johnson, who also has responsibility for public sector pensions, told TUC delegates that changes to the retirement age would still mean "high-quality" provision.
It was important to give workers "a choice about when they retire, be it age 60 or 65 or later".
But any scheme had to be "capable of withstanding demographic changes."
Shadow Trade and Industry Secretary David Willetts said public sector pensions were "crying out for reform" but accused the government of "cynicism" in its handling of the matter.