The safety of London could be "fatally compromised" if police officers are not given time to rest and recuperate, a police leader has warned.
Sir Ian Blair has said his force is stretched
Glen Smyth, chairman of the Metropolitan Police Federation, said many officers had endured an exhausting regime since the bombings last month.
Mr Smyth suggested Police Community Support Officers (PCSOs) take on some security duties to relieve the burden.
Met chief Sir Ian Blair recently admitted his force is stretched.
Mr Smyth said the Met's response to the bombings had demonstrated the dedication and professionalism of London's police officers.
However, he said: "Many are working 12-hour shifts, day in, day out. Leave has been routinely cancelled and rest days scrubbed.
"Steps must be taken to allow them to rest and recuperate.
"If the prevailing situation is allowed to continue, the Met will become worn down to the point where its ability to protect London not only from terrorists but also from everyday robberies, burglaries, drunken disorder and other crime will be fatally compromised."
On Tuesday, Assistant Commissioner Tarique Ghaffur said work on major murder investigations had "slowed to a trickle", because so many specialist detectives had been moved to work on the bombings inquiry.
The cost of the anti-terrorism operation is thought to be in the region of £500,000 per day.
Mr Smyth also said "all stops" should be pulled out to increase the number of Met officers to its target of 35,000 for 2009.
He said the Met needed more properly trained and attested police officers as soon as possible and "no-one and nothing must be allowed to impede a rapid build-up of police officer strength".