The Government is facing the biggest outbreak of industrial unrest since the 1979 Winter of Discontent after members of the largest public sector union voted in favour of strikes in the bitter row over pensions.
Unison said its members, ranging from school dinner ladies and refuse collectors to social workers and NHS staff, backed a campaign of industrial action by 245,358 votes to 70,253, in a 29% turnout.
The union is now set to strike on November 30, when teachers, civil servants and other public sector workers will also be staging a walkout in protest at the Government's plans to increase pension contributions.
Over 220,000 teachers belonging to the NASUWT will start voting on Friday on industrial action, while other unions will announce the result of their ballots in the coming weeks.
The Government said Unison's voting figures showed there was "extremely limited support" for strikes, adding that the NHS had contingency plans in place to ensure quality of patient care was not compromised.
Downing Street said the strike vote was "disappointing, unnecessary and potentially damaging". A No 10 spokeswoman said: "We have a good deal on the table - one that is fair and affordable - and we would urge the trade unions to reconsider and look at the deal on the table."
Unison's ballot was the biggest in union history, with 1.1 million voting papers sent to its members, including nurses, teaching assistants, social workers, care assistants, paramedics, police staff, school dinner ladies, probation officers, cleaners and other public sector employees.
General secretary Dave Prentis said: "The decisive 'yes' vote in the ballot reflects the deep concern that our members have over Government ministers' proposals for their pensions.
"Yesterday's statement in Parliament was a marked improvement on earlier proposals. But it is important to understand that the statement has to be translated into offers in the scheme specific talks."
Unison said its members in local government voted by 171,428 in favour of strikes, with 54,500 against, in a turnout of 30%, while NHS workers backed action by 73,930 to 15,753 in a 25% turnout. Union officials speculated that between two and three million public sector workers could be on strike on November 30, making it the biggest day of industrial action since the Winter of Discontent in 1979 and even rivalling the 1926 General strike.