Conservative MP Dean Del Mastro is offering new information in his defence against allegations he spent too much money in his 2008 election campaign, arguing he didn't contract $21,000 in services from Holinshed Research Group.

Del Mastro has been under fire since a news report last week said Elections Canada is investigating him for exceeding federal campaign spending limits.

The MP has maintained he didn't go over his campaign spending limit. The punishment for breaking federal election spending laws is a maximum $5,000 fine or five-year prison sentence.

Del Mastro told CBC News Tuesday people are confused because of a quote for services that his campaign paid by mistake, which was refunded, and a less expensive invoice issued the same day by the same company. That invoice, for $1,500 plus GST, was paid and included in his campaign filings.

"The campaign never incurred a $21,000 expenditure from Holinshed research. Did not," he told CBC News.

"As I've indicated, the campaign did hire Mr. [Frank] Hall and his company and was invoiced $1,500 for a limited amount of work they did during the campaign. That is reflected in our campaign [records] and I was refunded for that."

Campaign manager issued cheques based on quote

A document filed in court and in his election expenses file indicates Del Mastro's campaign manager approved $21,000 in payments to Holinshed Research Group for 630 hours of election campaign phone calls, as well as get-out-the-vote services on the day Canadians went to the polls.

That cost wasn't included in the list of expenses Del Mastro provided to Elections Canada, which show he spent $90,987.52 or 98.29 per cent of his cap.

Del Mastro says that's because it was a quote, not an invoice, albeit one his campaign manager, John McNutt, signed off on and submitted payment in two instalments. The quote is dated Sept. 14, 2008, with McNutt's signature and a note about the payment dated the next day.

Del Mastro says the invoice for $1,575 reflects the services actually provided to the campaign. That invoice is dated Sept. 14, 2008, the same day as the quote.

The campaign expense report shows a $1,575 charge — $1,500 plus GST — for election surveys and other research.

While the initial statement of campaign expenses filed by Del Mastro's campaign lists the $1,575 charge, the updated statement also shows a $10,000 expense for Holinshed. There is no invoice for the $10,000 charge included in the expenses.

Elections Canada reviews every candidate's expenses and provides two sets of documents on its website: the data as submitted and the data as reviewed, which "may include updates to the original return ... and minor corrections made by Elections Canada," the agency explains.

Confusion over $21,000

The campaign's $21,000 payment was made in two chunks: one $10,000 cheque, which Holinshed refunded, and an $11,000 cheque dated one week later, which was cancelled, documents provided to Elections Canada show.

But Del Mastro's explanation doesn't clear up why he wrote a personal cheque for $21,000 to Holinshed just weeks before the election was called. The cheque, dated Aug. 18, 2008, was filed as part of a small claims court case. The suit, filed by Frank Hall, Holinshed's president, was dismissed as abandoned when Hall didn't pursue a court date.

Federal election spending laws say candidates can contribute $2,100 to their campaigns, a 10th of the amount in the personal cheque. Del Mastro doesn't directly address that cheque, but says all his election spending was reimbursed by the campaign.

The documents show Del Mastro and Hall tried to continue their business relationship, but disagreed about the scope of the work to be delivered and the payments. They signed a contract in April 2009, but Del Mastro terminated it five months later.

"I've got somebody that sought to receive additional funds from me for products and services that, if you have the civil case, you know I contended that we never received any products and services from Mr. Hall, that he never delivered on what he promised and that was the basis of my defence," Del Mastro said.

Holinshed, which was based in Ottawa, is no longer in business.

It's Elections Canada policy not to confirm or deny investigations.