A long-running pay dispute could force London police officers to demand the right to strike, a union has warned.
Police last went on strike in 1919
The Metropolitan Police Federation, representing 30,000 officers in the capital, said a Government-proposed deal means "pay cuts in real terms".
Chairman Glen Smyth said other Police Federation branches around the country were also "simmering with outrage".
The Home Office said the issue would now go to arbitration or conciliation.
Mr Smyth said: "If they continue to treat us in this cavalier fashion and this offhand way, they can expect we will challenge our ability to take industrial action."
He added that the Government's stance was a "real slap in the face".
He said Home Secretary Jacqui Smith should not think police officers would "swallow the insult" of being told their pay claims would not be met because "the Government doesn't think that their professionalism, dedication and often downright bravery is worth very much".
He added that if the dispute continued police officers would consider overturning their ban on striking.
The current pay agreement, dating from 1979, grants rank-and-file police officers index-linked increases based on pay awards to other public-sector workers, in compensation for the fact that police officers are banned from going on strike.
But the official side of the Police Negotiating Board - which represents the Home Office and police chiefs - has been trying to renegotiate the agreement.
A Home Office spokesman said pay negotiations were continuing, adding: "The Government recognises the vital and hard work which police officers carry out every day.
"That's why pay has increased by over a third in the last 10 years - 36% to be precise. That's 10% above inflation.
"Pay arrangements must be fair and affordable for the police service and for the taxpayer.
"A police constable at the top of their scale gets over £7,000 more than a nurse at the top of their scale."
British police officers last went on strike in 1919 over pay grievances dating back to Victorian times and have been barred from industrial action ever