Adam Giambrone in a YouTube video released a few days before officially entering the race for mayor of Toronto. (YouTube)

TTC Chair Adam Giambrone will stay in the race for Toronto's mayoralty despite his admission that he has been involved in an "inappropriate relationship with a young woman."

Giambrone, who officially launched his campaign for mayor just last week, said in a statement to the Toronto Star that the relationship "consisted of text messages and conversations in public places only."

At his campaign launch Giambrone was accompanied by Sarah McQuarrie, described as his longtime partner.

But Kristen Lucas, 20, said Giambrone told her McQuarrie was by his side for "political" reasons only. Lucas said the two have been having a relationship for more than a year and, according to the Star, "on several occasions, [they] had sex late at night on a couch in [Giambrone's] City Hall office."

The 32-year-old city councillor said in his statement that he had committed a "serious lapse in judgment" and offered apologies to "my partner, Sarah, my family and friends for the pain and embarrassment my indiscretion will cause them."

Giambrone's campaign manager, John Laschinger, told CBC News he expects the 32-year-old councillor will stay in the race despite the revelations.

"In this day and age the public expects our politicians to be frank, straightforward and transparent — and he's done that, as painful as it was. He's received a lot of messages of sympathy and support for him and for Sarah. Now we're getting on with running the campaign," said Laschinger.

It's not the first time a Toronto politician has been caught in a sex scandal. In 2000, former mayor Mel Lastman admitted to a 14-year affair with a woman who had once been an employee and who said he had fathered two sons with her.

Attempts by CBC News to contact Giambrone have not been successful.