Members of a union representing up to 1.3 million workers have voted in favour of joining strike action on November 30.
Unison , which represents staff ranging from social workers to school dinner ladies, balloted its members on whether to stage a walk out in a dispute over pension reform.
The union said 245,358 voted in favour, with 70,253 voting against.
This suggests less than a quarter of the potential number of voters back industrial action.
Unison had mounted a campaign calling on its supporters to vote in favour of a strike.
The other public sector unions will announce over the next few weeks if their members will take part in industrial action that day. The NASUWT teaching union will poll its members from Friday.
It comes despite talks between ministers and union chiefs on Wednesday that aimed to avert the day of action, which could cause significant disruption across the country.
The Government tabled a revised offer, compromising on some but not all of the issues considered contentious by the unions.
TUC general secretary Brendan Barber, who took part in the negotiations, said while he "welcomed" the new terms, plans for industrial action "remain unchanged".
"We are determined to secure a fair deal, pensions justice, for the workers we represent," he said.
He said they want to negotiate "but as things stand, unions are absolutely firmly committed to our plans for November 30.
"That will be a day on which millions of people will show their anger that they feel they're not being treated with fairness and justice in terms of these very damaging changes the Government intends to make to people's pensions," he added.
The GMB union said it too "welcomed" the latest offer from the Government but warned it may be "too little too late".
Sticking points for the unions remain the Government's position on increasing contributions, raising the pension age and linking pensions to the typically-lower CPI index of inflation rather than RPI.
Ministers including Chief Secretary to the Treasury Danny Alexander appealed directly to workers and urged them to accept the deal on the table.
He said the compromises would only stand if the unions accepted. If they go ahead with a walk-out on November 30, the Government could withdraw its offer, he suggested.
Mr Alexander said he understood families were facing financial pressures during tough economic times.
But reform was essential because the cost of funding pensions had risen dramatically to £32bn a year, he said.
"The bottom line is that we are all living longer."
The updated offer to union chiefs would see an increase to the cost ceiling, so future schemes would be based on a pension to the value of 1/60th of average salary accruing for each year worked.
This is 8% higher than under the previous offer.
A teacher retiring on a salary of £37,000 would receive a pension of £25,000 - compared to £19,100 under the current final salary scheme, he told the Commons.
A nurse retiring on £34,200 would receive £22,800 compared to £17,300, he added
Is the country not in enough shit????
