Prime Minister Justin Trudeau broke his silence today on the latest twist in the Aga Khan scandal, saying he received an overnight bag from the billionaire Ismaili Muslim leader during his vacation on his private island in the Bahamas.

In exchange, Trudeau gave the Aga Khan a sweater, the prime minister said during a raucous exchange with Conservatives in the House of Commons.

He refused, however, to say what happened to the gifts — whether he kept them, returned them, repaid their value or for‎feited them to the Crown.

Prime Minister Justin Trudeau tells Opposition Leader Andrew Scheer what gift he received from the Aga Khan 0:36

The Prime Minister's Office also has not yet responded to questions from CBC News about the brands of the gifts, their estimated value and whether the Aga Khan gave gifts to other members of the Trudeau family.

However, early Tuesday evening the PMO did reveal that Trudeau and his family declared the gifts to the Canada Border Service Agency when they returned to Canada, and said that the value of the gifts was below the threshold for the requirement to pay duty.

After a trip of seven days or more, Canadians can bring goods worth up to $800 back to Canada without having to pay duty or taxes.

Trudeau's answer came after opposition MPs went on the attack Tuesday, demanding to know what gifts Trudeau received during his controversial family vacation with the Aga Khan in December 2016.

"Not only did the prime minister accept an illegal trip to a private island, he went there and received additional gifts form someone who is actively lobbying the government," said Conservative Leader Andrew Scheer.

"Will the prime minister come clean and tell Canadians, did he return those illegal and unacceptable gifts before he could be lobbied again?"

Speaking after question period, Scheer said unanswered questions remain about the exchange of gifts.

"He still hasn't told us why he hid that from Canadians for so long, and as far as I know he still hasn't indicated the value of them either."

Trudeau's initial refusal to reveal the nature of the gifts or their value shines a spotlight on an apparent loophole in the federal government's ethics rules.

Trudeau's office initially said he didn't have to tell Canadians about the Christmas gifts he and the Aga Khan exchanged because he'd already told Canada's ethics commissioner about them.

However, the ethics commissioner's office said information about those gifts won't be listed in its public registry because Trudeau accepted an unacceptable gift from the Aga Khan.

"The public registry generally includes only acceptable gifts within the meaning of Section 11 of the Act," said Margot Booth, a spokeswoman for the Conflict of Interest and Ethics Commissioner's office.

"Unacceptable gifts do not trigger the Act's disclosure requirement and would likely be addressed in an examination, as was the case with Mr. Trudeau's vacation stay on the Aga Khan's private island."

The examination by former ethics commissioner Mary Dawson found that Trudeau violated Canada's ethics rules when he and his family accepted the Aga Khan's invitation to vacation over the Christmas holidays in December 2016 on Bell Island in the Bahamas, also known as Bells Cay.

Terrace overlooking the turquoise blue waters of the Exumas chain of Islands in the Bahamas. (CBC)

Dawson ruled that the trip was an unacceptable gift because the Aga Khan had dealings with the federal government, and Trudeau's relationship with him was not close enough to qualify as a friendship.

Dawson's report also revealed that Trudeau and his family exchanged gifts with the Aga Khan but did not disclose the nature or the value of the gifts.

"From December 26, 2016 to January 4, 2017, Mr. Trudeau and his family, and their friends spent their Christmas holidays on Bells Cay along with the Aga Khan, his children and their families," Dawson wrote. "The Trudeau family exchanged Christmas gifts with the Aga Khan and his family."

Beyond that, though, little is known about the gifts that the Aga Khan — a billionaire and leader of the world's Ismaili Muslims — gave Canada's prime minister.

Officials with the Aga Khan referred questions from CBC News to the Prime Minister's Office. The PMO referred questions from CBC News to the ethics commissioner's office.

Until Tuesday, Trudeau also was refusing to tell Parliament about the gift exchange.

"The prime minister disclosed any gifts to the conflict of Interest and ethics commissioner as part of her examination," the PMO wrote in its answer to an order paper question posed by Conservative MP Kevin Waugh.

"Following the commissioner's report, which is publicly available, the prime minister accepted its findings and followed all of the commissioner's recommendations and will continue to do so."

The ethics commissioner's office won't disclose the nature or the value of the gifts, saying it can't reveal anything beyond what Dawson put in her report.

Officials in the ethics commissioner's office acknowledge that there are limits to what they can do when a member of Parliament accepts an unacceptable gift.

"The Conflict of Interest Act does not provide for any measures to be taken when gifts have been found to be unacceptable following an examination," said Booth. "The only direct result of an examination report is shedding light on the activity examined."

Nor does the ethics commissioner have the power to order that an unacceptable gift be repaid or returned.

Testifying before parliamentary committee earlier this year, Dawson's successor Mario Dion suggested he be given that power.

"As it stands, I have no power to make recommendations in my examination reports, including the power to recommend that an improper gift be repaid," he told MPs.

"As suggested during my appearance before the committee, I believe that the committee should consider giving me the power to make relevant recommendations in my reports. Such recommendations would be specific to each situation, including recommending that individuals reimburse the value of gifts improperly accepted."

Duff Conacher, co-founder of the government ethics watchdog group Democracy Watch, said he believes that the ethics commissioner does have the power under Section 30 of the Conflict of Interest Act to order an MP to return a gift.

"It is clear that the ethics commissioner is fully empowered to issue a Section 30 compliance order to Trudeau ordering him to return any gift that the ethics commissioner has concluded 'might reasonably be seen to have been given to influence the public office holder in the exercise of an official power, duty or function.'"

Conacher also called into question the assertion by the ethics commissioner's office that unacceptable gifts aren't supposed to be included in the public registry, saying every gift worth more than $200 is supposed to be declared.

"That subsection does not exempt unacceptable gifts in any way, shape or form and it is completely unjustifiable for the ethics commissioner to claim it does."

Elizabeth Thompson can be reached at elizabeth.thompson@cbc.ca