Tory support is at slightly below a third of decided voters in the latest EKOS poll.

Prime Minister Stephen Harper's Conservatives continue to hold the edge over the Liberals among decided voters, a new poll suggests, even as the leaders of both parties suffer from dismal approval ratings.

The Tories garnered 31.9 per cent support in the survey to the Liberals' 26.6 per cent. The New Democratic Party was at 17.6 per cent, the Greens at 10.9 per cent and the Bloc Québécois at 9.7 per cent.

The poll, by research firm EKOS, was released exclusively to CBC News on Thursday.

It shows only slight changes from last week's tally, which gave the Conservatives 31.7 per cent, the Liberals 27.1 per cent and the NDP 16.3 per cent.

And it suggests regional voter preferences remain static, with the Tories finding their greatest backing in the Prairies and the Liberals in Ontario and Atlantic Canada.

The Conservatives continue to be the leading party among men and older Canadians, while the Liberals draw disproportionate support from university-educated voters.

The NDP's core constituencies are in British Columbia and Ontario, with only minor variations across age brackets or education levels, the poll suggests.

Ignatieff's approval sliding

Asked whether they approved or disapproved of the way Harper and Liberal Leader Michael Ignatieff are doing their jobs, nearly half of respondents in each case panned the party chief's performance.

Harper's job-approval rating stood at 33 per cent, consistent with poll results reaching back to last year. Only a fifth of respondents thought Ignatieff is doing well in his post, as his approval ratings continue to slide.

NDP Leader Jack Layton had the highest approval at 43 per cent, compared with 26 per cent of those surveyed who disliked the job he's doing.

Respondents were also asked whether they approved of U.S. President Barack Obama's performance; 70 per cent said they did.

For the poll, EKOS queried 2,303 people by phone between April 21 and April 27. The main voter-intention results are considered accurate to within two percentage points, 19 times out of 20.