London - More than 30 000 off-duty police officers marched through London on Thursday and hundreds of thousands of British public sector workers went on strike over the government's austerity measures.
Immigration staff, civil servants, health workers, lecturers and prison officers also took part in the 24-hour strike, the latest in a series of stoppages since the coalition government came to power two years ago.
Police officers from all 43 forces in England and Wales donned black baseball caps emblazoned with the words "Cuts are criminal" as they protested in London against the spending cuts and changes to their pay and pensions.
The police, who under British law are banned from holding strikes, warned that the government's push to cut a record deficit was putting public safety at risk.
Police Federation chairman Paul McKeever said in a speech: "We care very deeply about the communities that we serve. We have seen what happens when we have a government that has given policing a very low priority.
"If you are cutting our jobs, then you are cutting the service we can deliver and the public's safety is at risk."
London's Metropolitan Police said more than 32 000 police took part in the march.
One of those demonstrating, Andy Springthorpe, 47, a sergeant with West Midlands Police which covers Britain's second city of Birmingham, said he had wider concerns than how the cuts would affect him personally.
He said: "It's not just about our pensions, it's about the changes the government wants to impose that will fundamentally change the way we police our communities.
"Why repair something that isn't broken? It's very frustrating."
The government says the current pension provisions are unfair and unsustainable because people are living longer.
But trade unions say the plans will force their members to pay more and work longer for lower pensions.
Unions said more than 400 000 people were on strike, but Francis Maude, the Minister for the Cabinet Office, said the figure was "wildly inaccurate" and only about 150 000 civil servants had taken part in the "futile" action.
Maude said: "The combination of the dedicated majority of public service workers who came to work as usual and our rigorous contingency plans ensured that public services were mainly unaffected.
"It is now time that union leaders put the best interests of their members first by asking them to accept our generous offer."
The action on Thursday was far smaller than the strike over pensions by up to two million public sector workers in November.
Prime Minister David Cameron's Conservatives and their Liberal Democrat junior partners in the coalition took a beating in mid-term local elections one week ago.
The results added to worries for Cameron after voters in France and Greece moved decisively against austerity in weekend elections.
Setting out its policies for the coming year in the Queen's Speech on Wednesday, the coalition said economic growth was one of its priorities.
But the speech added that "the first priority will be to reduce the deficit and restore economic stability".