A celebrated operation by Scotland Yard to seize uninsured vehicles fell short of expectations leading to a £1.3 million budget hole.
A change in the law allowed any officer the power to act on vehicles found without the correct paperwork, leading to the launch of Operation Reclaim.
It was thought the scheme would boost the force's coffers, get unsightly and polluting vehicle off the streets and cut crime.
But new figures revealed police expect to seize 36,000 vehicles by April, 24,000 fewer than anticipated.
As a result, the Metropolitan Police is bracing for a £1.3 million shortfall from the £3.2 million in fines and fees it was expected to collect.
Nevertheless, the force said the operation has been a success with far higher numbers of vehicles removed than in previous years.
Jenny Jones, a member of the Metropolitan Police Authority (MPA) who campaigns on road safety, said more work needs to be done to tackle uninsured drivers.
She said: "Two decades of neglecting this issue have led to a culture of lawless roads where far too many motorists in London feel they can drive without insurance and get away with it.
"It is staggering to think that in parts of London one in four road collisions leading to an injury involves a hit-and-run driver."
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