LONDON (Reuters) - Hundreds of thousands of public sector workers including teachers, council workers and firefighters staged a 24-hour pay strike on Thursday in a stoppage that has prompted Prime Minister David Cameron to pledge a crackdown on union powers.

Protesters marched through the streets of many of Britain’s main cities in one of the biggest co-ordinated labor stoppages for three years.

Denouncing what they called “poverty pay,” they demanded an end to restrictions on wage rises that have been imposed by the government over the past four years in an effort to help reduce Britain’s huge budget deficit.

In London, demonstrators marched towards Trafalgar Square at midday, chanting “Low pay, no way, no slave labor” to the beat of a drum. A giant pair of inflatable scissors, carried by members of the National Union of Teachers (NUT), read “Education cuts never heal.”

Firefighter Simon Amos, 47, marched wearing his uniform behind a flashing fire engine parading members of the Fire Brigades Union (FBU). “The government are making us pay more for our pension for it to be worth the same, and making us work longer,” he said.

The biggest public sector union involved, Unison, said early reports showed the strike had lead to 3,225 school closures with more than 1,000 others partially closed.

Refuse collectors, school support staff, cleaners, street sweepers, care workers, nursery assistants and social workers were joining the strike, it added.

Slideshow ( 4 images )

Hot spots, it said, included the North East, Wales and East Midlands where most council offices had closed, while more than 60 picket lines have closed most services in Newcastle.

“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,” said Unison General Secretary, Dave Prentis in a statement.

HARD TIMES

Britain’s coalition government has enforced a policy of pay restraint for public sector workers since coming to power in 2010, imposing a pay freeze until 2012 and then a one percent pay rise cap, resulting in a fall in income in real terms.

The Cabinet Office played down the impact of the strike, saying that most schools in England and Wales were open and that fire services were operating throughout the country.

On Wednesday, Cameron told parliament he planned to limit unions’ powers to call strikes.

Slideshow ( 4 images )

“How can it possibly be right for our children’s education to be disrupted by trade unions acting in this way” he said.

Tough new laws would be proposed in the Conservative manifesto for next year’s general election, he added.

These would include the introduction of a minimum threshold in the number of union members who need to take part in a strike ballot for it to be legal.

The manifesto could also back the introduction of a time limit on how long a vote in favor of industrial action would remain valid.

The NUT mandate for Thursday’s strike, for example, came from a 2012 strike ballot based on a turnout of just 27 percent, Cameron said.

The issue of minimum voting thresholds last arose three months ago when a strike by London Underground train drivers caused huge disruption in the capital, prompting Mayor Boris Johnson to demand that at least half of a union’s members should vote in favour for a strike to go ahead.