Over a million public sector workers are taking industrial action against the Government in a series of rows over pay, pensions, jobs, conditions and spending cuts, according to union leaders - a figure disputed by the Government.
Unions have hit out at Conservative plans to change strike balloting laws as "utter hypocrisy".
The Conservatives are drawing up plans to change employment law so that a threshold of those balloted would have to be reached before industrial action could be held.
But Unite said no Tory Cabinet member achieved a 50 percent voting threshold in the last general election.
General secretary Len McCluskey said: "It is utter hypocrisy for the Government to talk about mandates for trade unions when not a single member of the present Cabinet would have been elected using the same criteria.
"The fact is not a single councillor in England has won 50 percent of the electorate, not a single MEP has reached the 50 percent threshold, Boris Johnson scraped in with just 37 percent in 2008 and the Government's flagship police and crime commissioner election gained a risible 17 percent."
Union leaders said they were "overwhelmed" by support after a strike by public sector workers caused widespread disruption.
David Cameron, Michael Gove and other Government figures depicted in a variety of unflattering manners by striking public sector workers.
Hundreds of schools are to close tomorrow as teachers join strike action. Find out what schools in your area are affected.