The mayor of London's transport plans came under renewed fire after it emerged 26 million kilometres (16.2 million miles) of bus trips will go.
Boris Johnson's plan will see the bus subsidy slashed by 37%, resulting in the drop in journeys. It comes days after a 12.7% fare rise was announced.
London Assembly member Val Shawcross said it amounted to an "attack on the bus service and its passengers".
The mayor's office said it was "acutely aware of the value of bus services".
But Ms Shawcross said: "The proposed cuts to the bus service are deeply worrying and, along with his fare rises, contradict all the mayor has said about getting people out of their cars and on to public transport.
"A £150m cut to bus service subsidy means London's buses will be running 26 million fewer kilometres per year - while bus passengers can expect to pay above-inflation increases for their tickets.
"All this adds up to an attack on the bus service and its passengers who are clearly way down on the mayor's list of priorities."
'Dose of reality'
Mayor's transport advisor Kulveer Ranger said: "The mayor is acutely aware of the value of bus services to Londoners which is why, at a time when TfL's budget is under huge pressure from the recession, the collapse of Metronet and the volatile fares policy of the previous administration, he is ensuring that services are protected.
"We have to be realistic and for taxpayers' subsidy of the capital's bus services to leap from £24m in 2000 to £602m this year is simply not sustainable in these tough economic times."
Transport for London's business plan will see the total bus mileage drop to 478 million kilometres from last year's estimate of 503 million kilometres.
Mr Johnson's price increases were condemned in the House of Lords by Lord Faulkner of Worcester, Labour, who said: "Transport undertakings put their up fares for two reasons - either because they have to or because they choose to.
"In the case of the mayor, it is a fare increase entirely out of choice."
He added: "It would not have been necessary for fares to rise if not for the scrapping of the congestion charge extension, which would have raised £50m, the dropping of plans to impose additional charge on polluting vehicles and the crazy scheme to abolish bendy buses."
Responding Mr Ranger said: "The fact is that the mayor has taken strong and decisive action to introduce a much needed dose of reality and correct the mistakes of the past".