Canada has formalised its withdrawal from the UN tourism body after Zimbabwean president Robert Mugabe was invited to become a global leader in the sphere and sent a letter in recognition of Zimbabwe's co-hosting of the organisation's general assembly next year.

John Baird, the Canadian foreign minister, said the correspondence by the UN world tourism office (UNWTO), in which its secretary general reportedly praised Mugabe and the president of Zambia, Michael Sata, on Tuesday for their role in tourism at Victoria Falls, was the "last straw" in the country's participation.

"After [Baird] heard that [Mugabe] was honoured at an event, after he was invited to join this global leaders group, he signed the order in council almost immediately," said Joseph Lavoie, spokesman for Baird, referring to the mechanism needed to formalise Canada's notice period.

He added: "They were legitimising him by enlisting Mugabe to promote tourism."

The UNWTO disputed Canada's reasoning, pointing out that Mugabe had not – as had been claimed – been appointed as a special ambassador for tourism or given any special title.

In a statement, the body said it did not have an ambassadorial programme and the event at Victoria Falls had been held in order for an agreement to be signed by the UNWTO, Zimbabwe and Zambia to permit the hosting of the general assembly at the waterfall, which straddles the borders of both countries.

It added that the letter sent to the Zimbabwean president had also been sent to the leaders of other countries as part of the UNWTO's "global leaders for tourism" campaign. "This letter was sent to all heads of state and government worldwide and aims to raise awareness of the potential of tourism for development, job creation and economic growth," it said.

Mugabe, 88, is under a US and EU travel ban because of alleged human rights abuses in Zimbabwe. His tourism minister, Walter Mzembi, was quoted as brushing off Canada's snub as an inconsequential move by a "small player in the global tourism industry".

"It is not a player in the sector. It wants to leverage on the Mugabe brand. They want to take advantage of the Mugabe brand to be on the global map," Mzembi was quoted as saying on NewZimbabwe.com. "If they want to withdraw, let's go ahead."