Met chiefs in South London - responsible for patrolling many of the capital's most crime-plagued bus routes - are said to be "furious" and fear the cost of routine investigations will soar.
Transport for London (TfL) chiefs stunned senior officers when they tabled the proposals on behalf of bus companies including Go Ahead, Arriva and Metroline at a behind closed-doors meeting.
A highly-placed Met source told the South London Press: "It's absolutely outrageous.When it was brought up at a public meeting we couldn't believe our ears.
"We already spend vast amounts of taxpayers' money policing the buses and protecting passengers.
"CCTV is a vital part of that because it gives us compelling evidence to put before a jury - evidence that helps put thugs,violent criminals and vandals behind bars.
"It beggars belief that these profit-making firms now want to send us the bill for protecting their customers."
High-quality CCTV footage is seen as a vital weapon in the drive to identify offenders and stem crime on and around buses.
It helped convict deranged killer Peter Kelly, 28, who stabbed Bartosz Dlugowszewski in front of horrified passengers on a double-decker in Bermondsey.
And the 14-year-old knifeman pictured, above right, on a bus in Kennington was caught when a reader shopped him the day after this crystal-clear image was printed in the South London Press.
Cops have to study every possible CCTV sequence available because, without it, defence lawyers can accuse them of not exhausting all possible lines of inquiry.
Go Ahead - which operates buses from nine garages in central and South London - argued it was reasonable to bill police £50 an hour for collecting footage in a "small number of cases".
The firm said it processed 3,700 segments a year for the Met, with each download taking about 45 minutes.
Andrew Smith, Go Ahead risk and safety manager, said: "Where the police require CCTV from a number of buses for one investigation we may have to make a charge to the police due to staff having to be diverted from other duties to provide the evidence."
Speaking for other bus firms in South London, a TfL spokesman said the Met had agreed in principle to the need for a charge.
He said: "Some of the bus operating companies have been bearing the costs of responding to out-ofhours and particularly time consuming requests from police for the retrieval of CCTV footage.
"Others have already set out a charging policy for such requests."
Glen Smyth, chairman of the Metropolitan Police Federation, branded bus firms' demands "unreasonable".
He said: "They have a duty to assist the police and I would have thought it was in their commercial interest to do everything possible to ensure the safety of passengers.
"At the end of the day we can seize footage anyway in the same way we would seize someone's computer if we felt it contained evidence.
"But we should be working together - not against each other."