Labour-affiliated trade union Unison has confirmed strike action on 30th November, despite less than a quarter of balloted members actually voting to strike.
Of the 1.1 million balloted Unison members in the public sector, less than 22 per cent voted in favour of the action.
The union, whose donations make up eight per cent of Labour's union coffers, threw its weight behind Ed Miliband during the Labour leadership contest in 2010.
Today, Co-Chairman of the Conservative Party Sayeeda Warsi has called on the Labour Leader to condemn the strikes or risk accusations of keeping quiet to please his paymasters.
Baroness Warsi said:
'Today's vote is very disappointing news for the families and businesses up and down the country who will be affected and inconvenienced by this unnecessary strike.
'This is especially disappointing given the very low turnout in support of striking. Given the Government's offer is now much improved, Unison should urgently be reconsidering their position.
'Ed Miliband's weakness remains his hallmark. He still refuses to condemn unjustified union strike action that will hurt our economy and cost jobs.
'And with Unison giving almost £1 of every £10 of Labour's trade union funding, it's clear he's keeping quiet to please his paymasters.'
Labour ministers including Ed Balls MP and Rachel Reeves MP have repeatedly refused to condemn strike action planned for this month - Shadow Treasury minister Reeves ducking the question six times on broadcasting yesterday.