Boris Johnson has said he kept 91% of his 2008 mayoral election pledges - contrasting the record to "broken promises" under Ken Livingstone.
Mr Livingstone was mayor from 2000 until 2008 and is challenging Mr Johnson in May's election for the role.
The mayor backed his claim with a 68-page report arguing that he kept 98 of his 108 pledges in 2008, making progress in five and breaking five.
Ken Livingstone's team accused Mr Johnson of spinning reality.
Mr Johnson said: "I promised to run the most open and transparent administration in Britain.
"That is why, with this brutally honest and unprecedented progress report, I am determined to level with Londoners.
"I have detailed where we have succeeded and if we have not achieved a goal then I am determined to be honest about the reason."
Mr Livingstone has made several high-profile election pledges, including lower Tube fares, the reinstatement of a weekly payment to poor youngsters for staying at school and money for childcare.
The Conservatives have questioned how London could afford the outlay at a time of parlous public finances.
And Mr Johnson said his rival broke numerous pledges last time he was in office, including on crime, transport fares and affordable housing.
He said: "It is easy to make promises - it is hard work to keep them.
"And it is vital Londoners can trust their mayor to deliver on what they said they will."
He challenged Mr Livingstone to publish a similar report detailing the promises he kept during his tenure.
A spokeswoman for Ken Livingstone said: "There is a huge gap between Boris Johnson's spin and the reality of everyday life in London with fare increases, police cuts and rising violent crime under the Tory mayor.
"Boris Johnson promised to negotiate a no-strike deal.
"But he has failed to even meet with the unions and as a result the number of strikes has risen."
'Not good enough'
The spokeswoman went on: "The Tory mayor has broken his promises on knife crime and cut police.
"Ken's pledges will help millions of Londoners."
Liberal Democrat mayoral candidate Brian Paddick said: "Under Boris Johnson, we have had riots in the streets, a rise in youth knife and gun crime, the cost of living soared, sky-rocketing fares and £11m spent on a bus.
"If he's delivered his manifesto, it clearly wasn't good enough in the first place."
Green Party election candidate Jenny Jones said: "2011 was one of the worst years for air pollution in London and a combination of mayoral backward steps and delays is partly to blame.
"For example, he has completely abandoned his pledge that all new buses would be hybrids.
"Boris made a lot of noise about reducing knife crime, yet the violence experienced by young people has increased every year since the mayor was elected."