OTTAWA -- Liberal leader Bob Rae sent another letter to Elections Canada on Tuesday to question "unusual" election donations and overspending by Conservative Peter Penashue in the 2011 election.

Penashue, who presently serves as Intergovernmental Affairs Minister, has been under fire for alleged corporate donations and overspending during his campaign in the riding of Labrador.

Campaign documents, obtained through Elections Canada, indicate Penashue had an arrangement with a Labrador airline to pay a $7,000 flat rate for flights to travel throughout the riding during the campaign.

Rae had distributed a letter from Elections Canada to the media on Sunday calling for a full probe into Penashue's campaign finances but he now says "additional facts" have become available.

"There is a group of five donations which were received on May 4, 2011, two days after election day, all from the same postal code," Rae said in the letter. "It is also the postal code for the corporate headquarters of Pennecon Limited. All five of the donors in question "¦ are officers of this company according to its corporate website."

Rae says this information suggests it is "prudent" for Elections Canada to investigate if rules were broken but the agency can't confirm if a probe is underway due to its policies.

The NDP has also slammed Penashue.

"Mr. Penashue's been found out for the fact that they buried $17,000 in flights," said NDP ethics critic Charlie Angus. "I think if the findings come back that they did overspend the limits, if they were hiding documents, if they did abuse this trust, Mr. Penashue has no business sitting at that cabinet table."

Penashue's former campaign manager, Reginald Bower, issued an apology this summer for oversights in Elections Canada paperwork after some overspending allegations came to light.

Bower has since received an appointment to oversee the federal-provincial board regulating Newfoundland's offshore oil sector but Penashue and the government have pinned the overspending oversights on him.