The ethics commissioner has rebuffed a request from a Conservative MP to investigate Fisheries Minister Dominic LeBlanc's decision to award a license for the Arctic surf clam fishery to a group with federal Liberal ties.

But Conservatives are now asking Mario Dion to take a second look at the deal — because they say they now have evidence that a member of LeBlanc's wife's family had a financial stake in the winning bid. The Conservatives claim that link may have influenced LeBlanc's decision — an suggestion the minister calls "ludicrous."

According to a letter obtained by CBC News, Mario Dion told Cariboo-Prince George MP Todd Doherty that he was imprecise in the wording of his initial request for an investigation, and cited sections of the conflict of interest code that would not apply to a decision made by a cabinet minister in his capacity as a minister of the Crown.

"As the decision taken by Minister LeBlanc was taken in his capacity as a minister rather than in relation to his parliamentary duties, the Code has no application in the present situation," Dion wrote in a letter marked "confidential."

"The information you provided is insufficient for my office to initiate an examination in the present circumstances."

Dion was recently named to the position by the Liberal government and confirmed by MPs late last year.

Doherty, the Conservative fisheries critic, alleges the government's effort to expand ownership in the fishery — by clawing back part of an existing quota held by Clearwater Foods and handing it to a group with Indigenous representation — violates the Commons conflict of interest code because it enriches the brother of a sitting Liberal MP and a former Liberal MP.

On Wednesday, Doherty said he has new questions after learning that a member of the minister's wife's family has ties to the winning bid. He accused LeBlanc of feathering his own nest in awarding the bid to this group.

"What we've also learned through these recently released documents is that Five Nations is headed by Gilles Thériault. Who is Gilles Thériault, you ask? None other than a cousin of the minister's wife," he said in question period, citing documents filed in Federal Court.

A spokesperson for LeBlanc confirmed Thériault is a cousin of LeBlanc's wife.

"Any notion that this was the reason for my decision is a baseless and ludicrous accusation. I made my decision for no other reason than to allow for increased Indigenous participation in the fishery. I reject any insinuation to the contrary in the strongest of terms," LeBlanc said in a statement to CBC News.

"Mr. Doherty is recklessly making personal accusations. I am proud of this decision and will continue to focus on how it will directly benefit First Nations communities across Atlantic Canada and Quebec."

A spokesperson for Conservative Leader Andrew Scheer said Doherty would soon resubmit his request for an ethics probe — this time citing the relevant sections of the code and the familial connection.

Dion said in his letter, dated May 8, that prior to the official complaint from Doherty, he undertook a review of his own after media reports circulated about Liberal links to the group that secured the lucrative licence.

"When the matter first became public in March 2018, I gathered information from public sources, which included information you provided in your letter. At that time, I found no reasonable grounds to believe that Minister LeBlanc would have contravened any of his obligations under the Act in relation to this situation," he wrote.

Conservatives are 'mud-slinging,' Trudeau says

The winning bid for the license was claimed by Five Nations Clam Company and its partner, Premium Seafoods. The latter company is controlled by Edgar Samson, the brother of Nova Scotia Liberal MP Darrell Samson. One of the Indigenous partners in the company, NunatuKavut, is presided over by former Liberal MP Todd Russell.

Doherty alleges that when the license was awarded in February 2018, the Indigenous-led Five Nations Clam Company didn't even exist and was simply an entity on paper.

"The minister personally intervened in the surf clam process. He ordered the department to award the lucrative contract to a group that didn't have a boat. They didn't have multiple First Nations partners. They weren't even incorporated," Doherty said Wednesday.

"What they did have was close family ties to the minister and to the Liberal Party. Does the prime minister think its appropriate that the minister is awarding million dollar contracts to Liberals and his own family members?"

Prime Minister Justin Trudeau said the Conservatives should take it up with the ethics commissioner if they believe there has been some sort of impropriety.

"We understand that for the Conservatives, mud-slinging is just a way of doing politics and personal attacks is all they seem to have to go on, because it's really hard to attack us on the number one growth record in the G7 and the creation of 600,000 new jobs," he said.

"They stick with the ethical attacks, which is fine, but Canadians need to know we have a conflict of interest and ethics commissioner there to look into the facts of the matter and make determinations."

In his letter, Dion said he understands the matter is now before the Federal Court; one of the losing Indigenous bidders for the license, Miawpukek Mi'kamawey Mawi'omi First Nation, is asking a judge to quash the decision. He said his office will monitor developments and inform Doherty "in due course if any new information leads me to initiate an examination under the Act."

The surf clam license is worth tens of millions of dollars. The group will now have a quota for 8,924 tonnes of the seafood delicacy, which is harvested in the waters off Nova Scotia and Newfoundland and Labrador and is often shipped to Asia for sushi.

Surf clam sales in the second quarter of 2017 hit $25 million.