A growing number of Canadians oppose the U.S. missile defence shield, a poll shows.

A new poll conducted for the Toronto Star suggests 54 per cent of Canadians oppose participation, up one percentage point from last October -- a sign that the shield could emerge as an election issue for the federal Liberals, the Star reported.

With a minority government and most Canadians opposing the program, the federal Liberals may feel pressed to reject U.S. President George Bush's proposition that Canada join the program.

The missile defence system should be operational in the United States by later this year. It is designed to defend that country from missiles fired from either rogue states or terrorist groups with access to a missile system.

"For Mr. Martin and the Liberals it's evolved from being a relatively benign issue to one that could be genuinely troubling," EKOS President Frank Graves told the Star.

"Moreover, people tell us that unlike other issues like same-sex (marriage) or ethics, this is an issue which may well be worth fighting an election over," he said.

Public support from the program has also decreased, 34 per cent of Canadians now support or strongly support the shield, as compared to 37 per cent last October.

Graves told the Star that public support has dropped by 20 percentage points in the last few years and that the decrease should be seen as an indicator of "deeper anxieties about what the American administration (is) doing."

"A couple of years ago it wasn't a particularly troubling issue. Most Canadians said 'Well, they're going to do it anyway, we might as well get onboard'," he said.

Support for the missile defence shield was highest among Conservatives at 57 per cent; Liberal support was at 33 per cent; and weakest among NDP and Bloc Quebecois voters.

Opposition is highest in Quebec, with 64 per cent of survey respondents against the program; compared to 57 per cent in British Columbia and 52 per cent in Ontario.

Women were more inclined to oppose the issue, with 59 per cent against the program compared to 50 per cent of men.

Earlier this week, Defence Minister Bill Graham said the idea of the missile defence shield is not dead in Canada, despite opposition from the Bloc Quebecois, NDP and within the Liberal caucus.

Critics have called it the first step toward the weaponization of space.

"We're considering exactly what is the appropriate answer to give on ballistic missile defence," Graham said.

"The whole object is to make sure that any participation in ballistic missile defence would be circumscribed by clear understanding that we're not participating in anything that would involve the weaponization of space or the use of Canadian territory."

Canada and the United States have already altered their NORAD agreement to share information with the missile defence authority.

But supporters say the Canadian government should join the program if it wants a say in its future.

"If Canada sits on the sidelines, it is clear that it will not have a voice or any influence over the future direction of the program," said the Conference of Defence Associations.

The matter is expected to be discussed at the Liberal party's Ottawa convention in early March.

EKOS surveyed 1,046 Canadians aged 18 and up from Feb. 7 to 9.

With files from The Canadian Press