With support for his party reaching unprecedented levels in some parts of the country, NDP Leader Jack Layton is being forced to defend so-called "ghost candidates."

During a campaign stop in Yellowknife on Thursday, Layton was asked about Ruth-Ellen Brosseau, an NDP candidate running in the francophone riding of Berthier-Maskinonge in Quebec. Brosseau travelled to Las Vegas on vacation in the middle of the campaign and is reportedly not fluent in French.

"I understand that's not true," Layton told reporters.

Brosseau had trouble holding a conversation in French with a reporter in Maskinoge, Que., and has been avoiding interviews with a local radio station there.

The New Democrats have been coming under fire for fielding candidates in Quebec or Ontario who have either taken time off the campaign trail for vacation or have avoided media interviews.

Layton was repeatedly asked about the matter while he was visiting Yellowknife to support the local NDP candidate, Dennis Bevington, whom the Conservatives have been criticizing for voting to dismantle the long-gun registry.

The NPD candidates "were doing their best," and some had family plans they couldn't change, Layton said. On the whole, he said his party has fielded the best and strongest team of candidates yet.

"Most of them are here, some of them had family plans they couldn't change, I'm very proud of this group," he said.

Layton's main rival in Quebec, Bloc Quebecois Leader Gilles Duceppe, didn't quite see it the same way.

"I'm not saying they aren't serious but it's not serious to be in Vegas, not serious to not be able to have a debate in French," he said.

There was a certain amount of irony in the exchange Thursday, as Layton called out Liberal Leader Michael Ignatieff during the English-language debate for failing to show up to Parliamentary votes.

The NDP has also released a list of Liberal candidates who avoided public debates during the campaign.

Thursday marked one of the few times Layton had a somewhat terse exchange with the media, as he faced a grilling the NDP leader usually doesn't get.

"So that you can ask your questions, I'll let you interrupt me as often as you want, but I'll try to answer as best as I can," he said to a large group of reporters.

"Can I finish a sentence?" he said at one point, somewhat frustrated.

Layton has been coming under increasing scrutiny from the media as well as from his political rivals thanks to poll numbers showing that support for his party is on the rise, in several regions. Across the country, the NDP are now polling second, not far behind the Conservatives.

On Wednesday, Layton said that vacationing candidates wouldn't be an issue if Prime Minister Stephen Harper had instituted fixed election dates as promised.

"A lot of families make plans and if we had fixed election dates that were being properly honoured -- we know Stephen Harper broke that law himself -- then it would be a lot easier for candidates to be able to make the plans to participate," Layton said.

After winning the 2006 federal election, the Harper government did set fixed election dates. But Harper called a snap election two years later.

With files from The Canadian Press