TORONTO (Reuters) - Canada’s minority Conservative government, which a few months ago seemed on the verge of having enough popular support to win a majority in Parliament, has seen its lead in one poll fall back to the lowest point since last summer.

Prime Minister Stephen Harper speaks during Question Period in the House of Commons on Parliament Hill in Ottawa in this December 9, 2009 file photo. REUTERS/Chris Wattie

An EKOS survey released on Thursday showed Conservative support at 33.1 percent, down 2.8 percentage points from the last EKOS poll on December 17, and support for the Liberals, the biggest opposition party at 27.8 percent, up 1.1 percent.

The Conservatives’ lead had been as high as 15 percentage points in mid-October, when voters reacted negatively to Liberal threats to trigger an election.

EKOS, which polled 1,744 Canadians in an automated telephone survey, said that no single issue has dragged down support for the Conservatives.

However, it said that the decision by Prime Minister Stephen Harper to suspend -- or prorogue -- Parliament until March, effectively shutting down opposition criticism, has added to the decline in the party’s popularity.

The opposition parties had been hammering away at the Conservatives over allegations that Afghan prisoners that the Canadian military handed over to Afghan authorities in 2006 and 2007 were subsequently tortured.

“Certainly, the prorogation maneuver is drawing near universal raspberries outside of the shrinking CPC (Conservative Party of Canada) base,” EKOS President Frank Graves said in a statement.

He added that the Conservative defections generally seemed to be going more to the left-of-center New Democratic Party (NDP) and the Green Party than to the Liberals, and it “may be that voters are still punishing the Liberals for their election threat.”

NDP support was at 16 percent in the poll, which was down 1 percent.

The poll said the Greens, which have no seats in Parliament, may be at a high water mark at 13.4 percent, “but if they can grow another point or two, they really will bear watching.” The Greens were up 2.2 percent from a week earlier.

The separatist Bloc Quebecois -- which runs only in the French-speaking province of Quebec -- was at 9.8 percent support, up 0.6 percent.

The EKOS survey was conducted between January 4 and January 5 and has a margin of error of plus or minus 2.4 percentage points 19 times out of 20.