The TUC general secretary, Brendan Barber, has said 2011 would be a "horrible" year of cuts.
In his New Year message the union boss claimed there would be cuts in jobs and real cuts in living standards.
He added the year could also be a tough one for the government, which may face further angry protests.
Meanwhile, another union leader, Mark Serwotka of the Public and Commercial Services Union said strikes next year were "inevitable".
"The more of us that stand together against the cuts, the more problems we can create. Unless you look like you want a fight, they won't negotiate," he told the Times newspaper, predicting that the disruption would begin in the spring. "The Government has to see we are serious."
The TUC's Mr Barber said a demonstration in London in March against spending cuts looked like being one of the biggest events his union had ever organised.
In his New Year message, he said: "It's hard to pick out the unkindest cut of all, but a top contender must be the 10% cut in housing benefit that kicks in after someone has been unemployed for more than a year."
The Times reported senior union figures would meet at a TUC meeting early in the New Year to discuss their response to the cuts.