Unions representing millions of British public sector workers threatened strike action over pay yesterday, warning Prime Minister Gordon Brown current policies could herald defeat for his government at the next election.

Firefighters, teachers and health workers joined a mass rally in central London opposite Parliament and lobbied lawmakers to persuade Mr Brown to offer higher public sector pay deals that match or beat inflation.

The unions, a core support base of the ruling Labour Party, said it was alienating the very people who brought it to power.

Mr Brown is battling to restore faith among voters squeezed by rising living costs and frustrated with his leadership and an 11-year-old government.

He must call an election by 2010 at the latest. Opinion polls and a drubbing for Labour in May 1 local polls put the opposition Conservatives on course to win.

Speaking to a packed rally, union leaders said their members' living standards were plummeting as food, fuel and housing costs soar while pay offers fail to match inflation.

"We didn't elect this government to rule this way, to watch its core supporters suffer and struggle," said Dave Prentis, president of the TUC, representing nearly seven million workers.

Noting the government's poor ratings, union leaders said they could force change in government policy if united.

Mark Serwotka, of the Public and Commercial Services Union which represents nearly 300,000 workers from coastguards to job centre staff, urged workers to consider industrial action.

"If Gordon Brown thinks he can march on and treat public sector workers in such a disgraceful way, think how he'd feel if he woke up one morning to headlines that said... dozens of unions representing millions of public sector workers all say we're going on strike the same day," he said.

"I predict that if we have the courage to do that, Gordon Brown will change his mind," he added, to huge applause.

Mr Brown's spokesman said there would be no retreat on pay, saying "difficult decisions" in recent years had helped keep inflation low, enabling the Bank of England to cut interest rates.

Ministers have negotiated multi-year pay deals for many public sector workers to keep inflation in check. Inflation is running at three per cent, one percentage point above the Bank of England's target, reducing room for further rate cuts.

Workers argue the deals equal a pay cut and accuse the government of using inflation statistics that do not convey huge rises in food, housing and fuel costs.

Unison - the largest healthcare union - voted on Friday to accept a three-year pay offer worth 8.1 per cent, bringing some relief to the government.

College lecturers in London, however, went on strike yesterday over pay and University and College Union General Secretary Sally Hunt said there would be more action across the country without a better pay offer.

The public sector threat comes on the back of protests by truck drivers and fishermen over high fuel prices.

National Health Service physiotherapist Sally Rudston, 35, said she was finding it difficult to make ends meet.

"It's really tough: Living costs, rent, petrol. Petrol is a big problem when we are working in the community visiting patients at home," she said on the sidelines of the rally.

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