A former Canadian diplomat says a letter from Prime Minister Justin Trudeau sent to senior diplomats earlier this week reaffirms the country's trust in its officials and shows a marked departure from the Harper government, which missed "a lot of opportunities" on the international stage.

Trudeau sent the letter Wednesday to the ambassadors and high commissioners of Canada's foreign missions, telling them a "new era" had begun for Canada's international relations, in which they will play a vital role.

In particular, Trudeau said he and his cabinet will rely on the diplomats' assessments and first-hand knowledge to advance Canada's foreign policy agenda.

Speaking to CTV News Channel on Saturday, former Canadian diplomat Colin Robertson called Trudeau's approach "very sensible."

"If the government is to achieve what is going to be an ambition foreign policy agenda, you need the people who will deliver it on your side," said Robertston.

"And so sending this letter to our ambassadors and high commissioners -- and essentially giving them freedom to do public diplomacy like the rest of the world -- is very positive sign."

Trudeau's handling of the nation's senior diplomats stands in opposition to the approach taken during Stephen's Harper leadership. Harper's Conservative government applied a policy of strict message control during his nearly 10-year tenure.

Robertson said that foreign policy was "tightly controlled from the centre" and officials would have to fill out forms called "message approval" that would be sent to the Department of Foreign Affairs, and eventually passed onto the Prime Minister's Office for final authorization.

The government also vetted the speeches, had the final say on meetings, and crafted detailed talking points for events taking place abroad.

Robertson said this policy of tight, centralized message control caused Canada's reputation to take a hit on the international stage.

"There were a lot of opportunities missed simply missed because of the time delay in which it took to get approval for high commissioners and ambassadors to speak," he said.

"You can do it in Canada where you're the one source of news, but when you're abroad -- where Canada is often striving to get some attention -- if an opportunity comes and you don't take it, it doesn't come again."

While Trudeau's letter did not specifically mention putting an end to Harper's policies, it did acknowledge that the senior envoys will be on the "frontlines of our diplomatic efforts."

It also stated envoys will have "a government that believes in you and will support you in your work around the world."

Trudeau further outlined a potentially expanded landscape for Canadian diplomacy.

"I expect that you will be engaged energetically in public diplomacy with other diplomats, host government officials, civil society, and the media -- in all manner of ways -- through direct contact, the media, and social media," he wrote.

Robertson said this could mean that officials will be encouraged to incorporate greater "experimentation" in the way that Canada diplomacy is undertaken.

"If you're going to have an aggressive foreign policy, particularly in a multilateral area, using all the tools that are now available makes a lot of sense," he said.

"And then trusting the judgement of our senior officers to use these tools appropriately -- mistakes will be made and they’ll have to be some tolerance for error. But far better to get out there and experiment to deliver the Canadian message than to sit sequestered at home."

With files from The Canadian Press