Police Community Support Officers, hailed as the future of policing in London, are at the centre of a row about their role.
The advert asks readers which one they would like to cut out
Full-page adverts taken out in two south-east London newspapers by the Metropolitan Police Federation ask for readers' views on community officers.
The federation, representing rank and file officers, says "real" officers are being replaced by the "new breed".
The ad calls on Londoners to vote for which they would rather cut.
Community officers were introduced to provide a high visibility, uniformed and reassuring presence on London's streets.
They are now operating in every London borough tackling low-level crime and anti-social behaviour.
However, in contrast with fully-trained police officers, they cannot arrest people, have only basic equipment and are advised to withdraw from violent situations, according to the federation.
Deputy Assistant Commissioner of the Metropolitan Police, Brian Paddick, said it was never an option to replace traditional officers.
"It does not make any sense to reduce the number of police officers in London," he said.
It is hoped to increase both the number of officers and community officers if the new budget is agreed and extra funding is allocated for terrorism, he said.
Glen Smyth, head of the federation, said: "It is a step too far if we reduce the number of officers fully-trained and fully-equipped and replace them by people who aren't fully trained and are not equipped and do not have powers."