OTTAWA - Veteran New Democrat MP Nathan Cullen is throwing his weight behind the leadership bid of upstart candidate Jagmeet Singh, a member of the Ontario legislature.

Cullen, who himself ran for the job against victor Tom Mulcair in 2012, says Singh's commitment to issues including electoral reform and climate change helped to cement his decision.

Cullen also says he is not concerned about the fact Singh lacks a seat in the House of Commons and may wait until 2019 to seek one.

Mulcair says it would be a "heck of a lot better" if his successor has a seat in the Commons in order to be able to do battle right away with the Liberals and Prime Minister Justin Trudeau.

Cullen, however, notes that even though the NDP was cheered for its work in the Commons prior to the 2015 election, it was Trudeau who triumphed despite spending less time on the floor of the House.

Voting for a new federal NDP leader got underway on Monday, with the winner to be declared sometime next month.