Toronto's integrity commissioner is investigating former mayor John Tory's self-described "inappropriate relationship" with someone who worked in his office.

Commissioner Jonathan Batty says Tory told him about the matter and asked him to review it on Feb. 10, the same day the former mayor announced he would be resigning.

Tory's scandal-tainted departure was made official Friday and sets the stage for a mayoral byelection, expected to take place in late spring or early summer.

Batty confirmed he was conducting an investigation but declined to answer a question about its scope.

When carrying out an inquiry, the integrity commissioner can summon evidence and examine witnesses under oath.

The mayor and city councillors are governed by a code of conduct, which says they should avoid real and apparent conflicts of interest and arrange their private affairs in a manner that promotes close public scrutiny.