The TUC backed co-ordinated strike action today by millions of public and private-sector workers fighting the Con-Dem attacks on pay and services.
Union delegates in Brighton rejected the coalition's failed austerity programme and pledged a massive struggle to save ordinary workers' jobs, pay and pensions.
Unison leader Dave Prentis said the Con-Dems had "declared war on our people" and promised to lead the fightback.
Congress roundly rejected the government's economic programme which has caused a double-dip recession, a stagnant economy and plummeting living standards.
Delegates vowed full support to all public and private-sector workers taking industrial action against cuts or attacks on pay, jobs, pensions or conditions and to co-ordinate unions in taking strike action.
Unions demanding "a future that works" pledged to campaign vigorously for an economic alternative and build to make the October 20 demonstration the biggest anti-cuts protest in British history.
Mr Prentis, whose union put forward the motion, said: "We are never stronger than when we co-ordinate action, when we speak with one voice.
"Yes, we will seek decent pay, fair pay. Yes, we will negotiate - that is what our membership expect us to do.
But make no mistake, if employers refuse to negotiate, if the attacks continue - we will deliver the co-ordinated action called for in this composite.
"October 20 has to be much more than just a march. It must be the launchpad for our campaign against austerity."
Public-sector workers are feeling the bite from the government's three-year pay freeze - just one front in the Con-Dem war on working people in which the NHS is being sold off, education privatised and other services slashed to the bone.
PCS general secretary Mark Serwotka said: "The government's austerity programme is the biggest attack on working-class people that this country has ever seen.
"We have to be fighting for a living wage. Labour's support for a public-sector pay freeze is shameful. The situation is appalling.
"We need October 20 to be the biggest demonstration we have ever seen.
"But PCS believes that the way to really shock the government is to follow up the demonstration as quickly as we can with mass co-ordinated strike action across the public and private sector."
Unite general secretary Len McCluskey agreed that the October 20 demo must be a "catalyst" for a wider campaign against failed Tory austerity - including "civil disobedience and strike action."
GMB regional secretary Tim Roache warned that the price of not fighting is more unemployment, worse pay and further attacks on the living standards of millions of people.
He said: "The misplaced idea that cuts work is wrong - they discourage recovery."
TUC delegates also backed a motion calling for a crackdown on tax avoidance and - for the first time ever - they supported full nationalisation of the banking sector.
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