Liberal MP Jim Peterson has announced his retirement from politics, leaving his Willowdale, Ont., seat vacant for recent party leadership candidate Martha Hall Findlay.

On Peterson's website, he posted a message Thursday saying he won't run in the next election.

His seat is expected to be handed to Hall Findlay without a nomination fight -- unlike fellow leadership candidates Bob Rae and Gerard Kennedy.

Rae announced his decision to return to Parliament on Canada AM Wednesday and filed his nomination papers later in the day.

He hopes to become the Liberal candidate in Toronto Centre, a riding currently held by Bill Graham, who announced last month he won't seek re-election.

Hall Findlay has already won a Liberal nomination twice -- first when she lost the race in Newmarket-Aurora to Belinda Stronach in the 2004 election, then again when she was asked to step aside when Stronach became a Liberal before the 2005 election.

Peterson, meanwhile, says he plans to pursue opportunities in the private sector and is also interested in teaching.

Peterson, 65, was first elected to Parliament in 1980, during the last Trudeau government. He was re-elected six times and served as international trade minister under former prime minister Paul Martin. He is credited with helping to open free-trade talks with South Korea.

The former lawyer and law professor -- who carried out the defection of ballet star Mikhail Baryshnikov in 1974 -- says he will continue living in Toronto. He wants to work on projects related to international trade and climate change.