Front-line police officers have voted overwhelmingly in favour of seeking the right to strike, angered by the government's failure to backdate last year's pay rise.

Tuesday's unprecedented announcement is an embarrassment for Gordon Brown coming just two days before the Crewe and Nantwich by-election which polls predict Labour is likely to lose.

The police row erupted in December when Home Secretary Jacqui Smith announced that a 2.5 percent pay rise, agreed by an independent tribunal, would not be backdated to September as expected.

The government said the decision was made to keep a lid on public spending and that the award was in line with other public sector increases.

But it left officers seething. They argued the rise was effectively only worth 1.9 percent and that Smith's decision was the first time a home secretary had failed to ratify their arbitration award in full.

Police said they suspected they were being picked on as they did not have the right to strike, prompting about 20,000 off-duty officers to march through London in the biggest police protest ever staged in Britain.

Meanwhile the Police Federation, which represents rank and file officers, balloted its 140,000 members on whether it should lobby for "full industrial rights".

Of the 60,572 officers who replied to the ballot, 86 percent supported this action, Jan Berry, the Federation chairman announced on Tuesday.

"I do not see this as a vote to strike -- yet," Berry told the Federation conference in Bournemouth, calling the vote "a wake-up call" for Brown.

"This says to me that police officers want binding independent arbitration," she added.

British police officers last went on strike in 1919 in a dispute over pay but have been barred from taking industrial action since the 1990s.

The current pay system dates back to 1979 and officers said Brown had broken the relationship that had existed since then.

"We are not happy because this government, led by Gordon Brown has lost the trust and respect of the police service in the United Kingdom," said Paul McKeever, chairman of the Federation's committee representing police sergeants.

"It demonstrates mind boggling incompetence," he told the conference.

That view was echoed by the Conservatives.

"The way the government have behaved towards the police is dishonourable and has destroyed the vital bond of trust that should exist between the police and government," said the party's home affairs spokesman David Davis.