OTTAWA - Stephen Harper's Conservatives have squandered their sizeable lead and are now statistically tied with the Liberals after weeks of stumbles, a new poll suggests.

The Decima poll, provided exclusively to The Canadian Press, indicates the Tories have slipped to 30 per cent -- putting them in a statistical tie with the Liberals who rose two points to 31 per cent.

But Decima's trend -- a trend borne out by other surveys -- brings little joy for the Liberals. While the Conservatives have been sagging, Stephane Dion's Liberals remain unable to capitalize on the governing Conservatives' struggles.

Just a month ago, the Tories were edging close to the 40-per-cent threshold needed to win a majority. Harper was winning plaudits for competence and decisiveness, his government's second budget was boosting the Tories' popularity and negative ads targetting Dion appeared to be having the desired effect of taking the lustre off the new Liberal leader.

But the Tories have since been hit by a series of controversies over their climate-change plan, the treatment of Afghan detainees, and the prime minister's taxpayer-funded image adviser.

They are now running marginally behind the Liberals, essentially back to where they were last fall and early winter. Conservative preparations for a spring election the prime minister insisted he did not want have come to a brisk halt.

"The Conservatives had come from behind to establish a lead and now that lead is gone,'' said Decima CEO Bruce Anderson.

Anderson noted that the Tories took heat last fall for their apparent indifference to global warming at a time when the environment was topping the list of voters' concerns. After regrouping and effectively neutralizing the issue during the winter, last week's sloppy launch of their new, much-maligned green plan seems to have set them back on their heels once again.

Parts of Environment Minister John Baird's new green plan were inadvertently faxed to the Liberals last week two days before they were supposed to be made public. The Conservatives were forced to defend their hard-won reputation for competence rather than concentrating on the contents of the plan.

"Last week probably didn't go as well as they'd hoped for and maybe that's putting it mildly,'' Anderson said.

Still, he said none of the opposition parties, including the Greens, seems to have a "singular advantage'' on the environment and, thus, none has been able to capitalize on the Tories' slide.

The NDP's support in the latest poll stood at 15 per cent and the Greens at 13 per cent.

In Quebec, the Bloc Quebecois led with 34 per cent to the Liberals' 21 per cent, the Tories' 18 per cent, the Green Party's 13 per cent and the NDP's 10 per cent.

In vote-rich Ontario, the Liberals led with 38 per cent to the Tories' 33 per cent, the NDP's 17 per cent and the Greens' 11 per cent.

Anderson said the poll may reflect "the new normal'' for both the Liberals and Conservatives, which is "not whether they can get to 40 (per cent) but whether they can sustain a number that's higher than 30 or 35.''

"And that obviously puts in question whether or not there's a majority government for anybody in the forseeable future.''

The telephone poll of just over 1,000 Canadians was conducted Thursday through Sunday and is considered accurate within 3.1 percentage points 19 times in 20.