Unions have hit back at Conservative plans to change balloting laws as "utter hypocrisy", pointing out the low proportion of the vote cabinet ministers got at the last election.
Schools across England and Wales closed and there was disruption to council services, museums and galleries, the fire service and jobcentres as more than a million workers took industrial action in bitter disputes over pay, pensions, jobs and spending cuts.
The action was hailed as the biggest strike over pay to hit the Government since it came to power in 2010.
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Home helps, lollipop men and women, refuse collectors, librarians, dinner ladies, parks attendants, council road safety officers, caretakers and cleaners walked out, alongside teachers, firefighters, civil servants and transport workers.
Picket lines were mounted outside courts, council offices, jobcentres, fire stations and Parliament in outpourings of anger over the coalition's public sector policies.
The action was hailed as the biggest strike over pay to hit the Government since it came to power in 2010.
The prime minister and other senior politicians attacked the strikes and 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% voting threshold in the last general election.
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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% of the electorate, not a single MEP has reached the 50% threshold, Boris Johnson (London mayor) scraped in with just 37% in 2008 and the government's flagship police and crime commissioner election gained a risible 17% of the vote.
"This government has no mandate to attack trade unions or the workers who have been forced to take industrial action today in their fight to end poverty pay."
Unite said that the Cabinet member with the lowest percentage of the vote was Welsh Secretary David Jones, who secured the support of 27% of the electorate in his seat of Clwyd West in 2010, and Culture Secretary Sajid Javid achieved a vote of 30.8% of the electorate in his constituency of Bromsgrove.
Welsh Secretary David Jones had the lowest share of the vote of any cabinet member, unions said
McCluskey added: "Britain's anti-trade union laws are already amongst the most restrictive in Europe.
"Tory attempts to further curtail the rights of working people to democratically organise risks placing Cameron's Britain alongside nations like Kazakhstan, Albania and Niger, where the right for public servants to take action is forbidden."
Unison general secretary Dave Prentis said: "It is a massive decision by local government and school support workers to sacrifice a day's pay by going on strike but today they are saying enough is enough.
"It is a scandal that people who educate and support children in schools, maintain crucial local services, keep our communities clean and safe places to live, and protect the homeless and vulnerable are not paid at least the Living Wage.
"We are calling on the local government employers to come back to the table and settle this dispute. Politicians from all parties have been talking about the need to end low pay and introduce the Living Wage, and they must get their own house in order first."
Members of Unison staged a demonstration outside Parliament, holding up giant "slices of bread" to symbolise that workers want more than a 1% slice of the pay bill.
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Mick Cash, acting general secretary of the Rail, Maritime and Transport union, warned of wildcat strikes if changes are made to balloting laws.
"If you remove the right to strike legally or make it almost impossible, then workers will, understandably, take matters into their own hands.
"If a majority of workers in a democratic, secret ballot decide to take action as last resort over their safety or jobs but the government or a judge says you can't do that because you've not reached a threshold or because this is an essential service, it is obvious how workers with a proud militant tradition will react.
"They will eventually take their own action and you will see highly disruptive wildcat action called at very short or no notice."
A Cabinet Office spokesman said: "The vast majority of dedicated public sector workers did not vote for today's action, and early indications are that most are turning up for work as usual.
"In the civil service we estimate that fewer than 90,000 members of the PCS union will not be working - this is lower than previous strike action, and just a fifth of the civil service workforce
"It is disappointing that, once again, some union leaders have pushed for strike action that will achieve nothing and benefit no one. Union leaders have relied on mandates for action that lack authority - the National Union of Teachers ballot was run nearly two years ago, while other ballots had extremely low turnouts."