TORONTO - Mayor David Miller says he will not ask Toronto Transit Commission Chairman Adam Giambrone to step down.

Giambrone dropped his bid for mayor of Toronto on Wednesday amid revelations he had "intimate relations" with women other than his live-in girlfriend.

"Adam Giambrone has stood before the people of Toronto, he has accepted responsibility for his actions and he's working with his partner on their private life and that's his private life," Miller told a news conference Thursday.

The mayor said he has confidence in Giambrone as chairman of the commission because he is doing a terrific job.

Transit ridership in the city is at its highest level ever, Miller said, noting the recession didn't cause numbers to plummet as past recessions did. He credited Giambrone for that success.

Changes led by Giambrone include making monthly passes transferable, which encourages people to share and ride transit, said Miller.

He said the biggest increase in bus service in the history of the transit system happened about a year ago. The system is also in the midst of replacing its bus and streetcar fleets.

Giambrone has taken responsibility for recent troubles with the transit system, Miller said.

Those troubles include photos and videos posted to the Internet of workers who appeared to be sleeping on the job or taking extended breaks as passengers waited.

"Giambrone has been leading a remarkable renaissance in public transit in Toronto. And it's got a little obscured because a couple of employees didn't perform properly," said Miller.