Union boss Len McCluskey has said he will "disregard" a new law to hold strikes with less than a 50 per cent ballot turnout, over public sector pay.
The general secretary of Unite, the UK's largest union, told the BBC that growing unrest could lead to mass industrial unrest and the “artificial threshold” imposed by the government in March would not stop him from leading coordinated action.
“If the government has pushed us outside the law, they will have to stand the consequences,” McCluskey said.
Action from public sector workers was “very likely and very much on the cards”, he added.
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.
“We support trade unions and the campaigns of people to get the public sector pay cap scrapped. It’s for the trade unions to decide what actions they take,” he said.
There is growing pressure on the government to lift the cap on public sector pay, and an announcement is widely expected this Wednesday. But it is thought this will only affect police and prison workers.
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.
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".