Prime Minister Justin Trudeau came under opposition attack on Tuesday, accused of misleading Canadians when he said he had to fly in the Aga Khan's helicopter during his controversial Bahamas vacation because it was the only way to travel to the billionaire's private island.

Opposition Leader Rona Ambrose led off the attack, demanding to know why he told Canadians the private helicopter was the only way to get to the island when a government employee arrived via seaplane.

"It's bad enough that the prime minister chose to vacation at one of the most expensive destinations in the world when taxpayers have to pay," Ambrose said during a raucous question period.

"But why did the prime minister tell Canadians a private helicopter was his only option when he knew it was against the law, against his own ethical guidelines — and now we find out it wasn't even true."

Opposition leader Rona Ambrose went on the attack Tuesday over Trudeau's Bahamas vacation. (Adrian Wyld/Canadian Press)

New Democrat MP Nathan Cullen also accused Trudeau of misleading Canadians and being above the rules.

"Today we learned that the prime minister's excuse is categorically false," Cullen told the House. "So does he wish to change his story or does he wish to continue to mislead Canadians?"

Trudeau, however, refused to directly answer the question, saying repeatedly that it was a private family vacation and that he will answer any questions that Conflict of Interest and Ethics Commissioner Mary Dawson may have.

He then suggested the decision to take the Aga Khan's helicopter was made by the RCMP.

"On prime ministerial travel, as is always the case, the RCMP makes determinations around what is the safest way for the prime minister to travel."

"Is he saying today then that the RCMP told him to break the law?" shot back Ambrose.

PM accused of misleading Canadians about helicopter to Aga Khan's Bahamas island. 1:31

Ethics investigation underway

Dawson is conducting an investigation following complaints about the trip and allegations that Trudeau violated government rules, which prohibit the prime minister, cabinet ministers and parliamentary secretaries from accepting free travel on non-commercial chartered or private aircraft without prior approval from the ethics commissioner.

Government rules also bar a prime minister from flying on a regular commercial flight for security reasons, meaning they generally travel on government planes. (During election campaigns, however, prime ministers generally travel on commercially chartered flights.)

This seaplane ferried a Privy Council technician from Nassau to the Aga Khan's private Bell Island. (Bahamasrentalvacations.com)

The attacks in the House of Commons came after CBC News revealed early Tuesday that a Privy Council technician who accompanied Trudeau to Bell Island travelled from Nassau on a commercially chartered seaplane.

CBC News also revealed that the cost to taxpayers for the trip was higher than was disclosed to Parliament.

While the government initially told Parliament that it cost more than $127,000, that total failed to include a charge of $6,695 for the commercially chartered seaplane flight, which brought over the Privy Council technician and 400 pounds of equipment.

The total tab, then, was more than $133,000.

A Privy Council technician accompanies prime ministers whenever they travel — for business or personal reasons — to ensure they have access to a secure office and secure communications.

'Personal family friend'

Trudeau has repeatedly come under fire in the House of Commons for the Bahamas trip and for his office's initial refusal to disclose where he was vacationing.

Fellow Liberal MP and longtime friend Seamus O'Regan and his husband, Steve Doussis, joined Trudeau's family on the island, along with Liberal Party President Anna Gainey and her husband, Tom Pitfield. Pitfield was a key member of Trudeau's election campaign team.

In January, O'Regan told the National Post that he and his husband also travelled on the Aga Khan's helicopter.

The Aga Khan's privately owned Bell Island is located in the Bahamas. (Google Maps)

Trudeau has defended the trip, arguing that the Aga Khan — a billionaire and leader of the world's Ismaili Muslims — is a longtime family friend.

However, the Aga Khan Foundation Canada, which lists the Aga Khan as its chairman in its most recent filings with the Canada Revenue Agency's charities section, has received federal government grants in the past for its international development projects. The foundation is currently registered to lobby several government offices, including the Prime Minister's Office.

On Jan. 12, Trudeau defended the decision to use the Aga Khan's helicopter, insisting it was the only way to get to Bell Island.

"The travel back and forth from Nassau to the island happens on the Aga Khan's private helicopter, which he offered us the use of," Trudeau told reporters in Kingston, Ont.

"The fact is, as I have said many times, the Aga Khan is a personal family friend, and travel to and from the island only happens through private means," he later added.