VANCOUVER - Liberal Leader Stephane Dion is dismissing any criticism within his party about a non-aggression deal struck with Green Leader Elizabeth May.

Dion has agreed not to run a Liberal candidate in May's Nova Scotia riding of Central Nova, which is currently held by Foreign Affairs Minister Peter MacKay.

In exchange, May is endorsing Dion as the best candidate to become prime minister.

Opinion within Liberal ranks is sharply divided. Some members offer lukewarm defence of Dion's decision, calling it a pragmatic strategic move. Others say it could further undermine Dion's shaky leadership and one senior party member told The Canadian Press that the deal was "colossally stupid."

But Dion doesn't seem fazed by the criticism.

"I think it's a good decision for my country, and for our role in the world," he said Saturday. "I'm very proud of what I have done."

Dion was vague about whether he'd rule out any other deals with the Greens.

"I'm just saying we have an agreement between leaders in each riding," he said, calling May's move "courageous."

"She has said she doesn't want to be the Ralph Nader of Canada," Dion said, referring to the perpetual American presidential candidate who has been accused of splitting the left-of-centre vote. "She wants me as leader of this country. It's for her to figure out how she will do that."

With the environment emerging as a major issue with the electorate - and hence with every party - Dion said having a Green member in the House of Commons is critical to the future of the planet.

"Facing exceptional problems, we need exceptional solutions," he said.

NDP Leader Jack Layton said it's undemocratic to deny the voters of Central Nova a full choice of candidates.

"Canadians don't like backroom deals between leaders and the kind of top-down gerrymandering that's going on here," he said.

Both Dion and Layton were in Vancouver for celebrations for the Sikh holiday of Vaisakhi.

Jewan Bassra, a Liberal party member attending Saturday's festivities, said that while he wouldn't be comfortable if such a deal was worked out in his Vancouver riding, he supports Dion's decision.

"I think the bigger picture is more important," he said. "If we can save our Earth, and save the environment and humankind, I think that's the best option for us."