OTTAWA - A new poll suggests the federal Conservatives have fallen three percentage points behind the Liberals in popular support, still within the survey's margin of error but a trend the Harper government would no doubt like to reverse.

The poll by Decima Research, provided exclusively to The Canadian Press, placed Liberal support at 32 per cent, the Conservatives at 29 and the NDP at 18. The Bloc Quebecois and Green party were tied nationally at nine per cent.

The telephone survey of just more than 1,000 Canadians was conducted from last Thursday until Monday.

Two days before the latest poll began, Nova Scotia MP Bill Casey was booted from the Conservative caucus for voting against a budget provision he says breaks a government promise on offshore oil revenues.

Because of small regional sample sizes, Decima averages results over three weeks of polling. The latest averages suggest the Liberals were six percentage points ahead of the Tories in Atlantic Canada -- 37-31 -- with the NDP at 20 per cent and the Greens at nine.

The poll also put the Liberals ahead in Ontario, 39-33, and had the Bloc rebounding in Quebec to 38 per cent, followed by the Liberals at 23 and the Conservatives at 16 per cent.

Decima CEO Bruce Anderson says the rolling averages suggest the Conservatives have lost ground in Quebec and Atlantic Canada, with Liberals getting most of the benefits.

The national numbers are considered accurate to within plus or minus 3.1 percentage points, 19 times in 20, while regional breakdowns have a wider margin of error of 6.2 percentage points.