TORONTO - Premier Dalton McGuinty has named Environment Minister John Gerretsen as Ontario's new interim minister of municipal affairs and housing.

Former minister Jim Watson confirmed today that he's quitting cabinet, and will resign as a member of the Ontario legislature shortly, to run for mayor of Ottawa.

Watson was Ottawa's mayor from 1997 to 2000, and was first elected to Queens' Park in the Liberal sweep of 2003.

Former deputy premier George Smitherman officially resigned last week to run for mayor of Toronto, prompting McGuinty to immediately call a byelection in Toronto Centre for Feb 4.

However, the premier has up to six months after a resignation to call a byelection and he is not expected to move as quickly to fill the Ottawa-West Nepean seat vacated by Watson.

McGuinty is expected to shuffle his cabinet next week to replace both Smitherman and Watson on a more permanent basis, but other significant changes are also expected.

"By departing provincial politics to seek election at the municipal level, Jim is demonstrating his belief in public service and commitment to improving the lives of families in my hometown of Ottawa," McGuinty said in a release Tuesday.