Public sector workers had a pay freeze for two years from 2010, thereafter with pay rises capped at one per cent, as part of the government's austerity drive.
Len McCluskey, the General Secretary of the Unite union which has more than 1.4 million members, also told BBC radio that he would be prepared to break tough new laws on industrial action. But it is thought this will only affect police and prison workers.
In 2011, hundreds of thousands of workers including teachers and civil servants went on strike over changes to pensions in what was the biggest walkout seen in Britain for a generation, although the said the impact was limited.
Under British law, any strike must be removed by a ballot involving at least 50% of the union's members.
But McCluskey said this was an "artificial threshold" and that "if the government have pushed us outside the law then they will have to stand the consequences".
The Labour Party has warned the government must fully fund a pay increase.
Unite may have tacit support from Labour, with shadow justice secretary, and former shadow City minister, Richard Burgon, refusing to be drawn on the matter despite being asked four times whether he would back illegal strike action.
Les South Winners interpellent le président Jacques-Henri Eyraud — OM
Marseille reste sur deux lourds revers, contre Monaco (1-6) et Rennes (1-3), et se déplace à Amiens dimanche (15h00). La colère monte chez les supporters marseillais.
"In relation to the question of turnouts in strike ballots, what we have always been supportive of is encouraging as many people to vote as possible".
Mr Burgon added that a co-ordinated strike would not be illegal.
During the TUC's conference this week, general secretary Frances O'Grady said action was a possibility if the government didn't act - but only as "a last resort".
"I'm very clear that people are angry and if we don't get that pay rise then the TUC is certainly ready to assist our unions and coordinate as we always do", O'Grady said.
The composite motion called for "immediate steps to develop a coordinated strategy of opposition to the pay cap ... including ... pay demands, campaign activities, tactics, ballots and industrial action".
Jeremy Corbyn will address the conference on Tuesday afternoon in Brighton, but he will be under pressure to say whether he would support breaking the law to challenge the government over the public sector pay cap. He told TUC delegates: "Wouldn't it be great if we could have coordinated ballots in the run-up to the budget".
He floated the idea of the Labour Party having a second deputy leader who would be a woman.
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