CUPE national president Paul Moist (left) announced his endorsement on Monday for NDP leadership candidate Greg Selinger (right). (CBC)  The head of the largest union in Canada is backing Greg Selinger's bid to become Manitoba NDP leader.

CUPE national president Paul Moist announced his endorsement on Monday, saying he has worked with Selinger since the latter's days as a Winnipeg city councillor. Moist said he knows Selinger can bring people together to get things done.

The provincial government's success in the past decade is the result of improved relations between business and labour, Moist said, adding Selinger is best suited to build on that success.

The Canadian Union of Public Employees has 600,000 members. Its Manitoba division contributes roughly 24,000 members to that total.

Selinger is running against Steve Ashton and Andrew Swan to become the next leader of the Manitoba NDP and immediately step into the role as premier.

Gary Doer, who has been the party leader since 1988 and the premier of Manitoba since 1999, surprised many political observers when he announced on Aug. 27 that he was stepping down. The next day he was introduced in Ottawa by Prime Minister Stephen Harper as Canada's next ambassador to the United States.

A leadership convention has been set for Oct. 16-17, with the new premier to be named on the final day.