An uninhabited island at the centre of a century-old Canada–US territorial dispute is back in the spotlight after a Canadian senator urged Ottawa to assert sovereignty over the piece of land.

Senator Jim Quinn from New Brunswick has taken issue with an American boat tour group that describes Machias Seal Island on its website as being “on the Maine Coast”.

He has called on Ottawa to review its permitting of the tour group to visit the island – home to thousands of puffins – as well as the mention of the group on a government website.

Machias Seal Island is a tiny, rugged island located in a disputed “Grey Zone” between the US state of Maine and the Canadian province of New Brunswick.

The tear-drop shaped island is a migratory bird sanctuary and is described as “one of the most important seabird nesting colonies” by the Canadian government. It is also home to one of the most southerly colonies of the Atlantic puffin.

• The only land disputed between the US and Canada

It has no permanent inhabitants, save for a rotating crew of Canadian Coast Guards who man a single lighthouse built there in1832 by Canada.

The Canadian government lists two tour groups that are permitted to visit the island — Canadian company SeaWatch Tours, and the US-based Bold Coast Charter Company.

On its website, Bold Coast states that it operates tours to “Machias Seal Island – Largest Puffin Colony on the Maine Coast”. It adds that its operations are authorised by the US Fish and Wildlife Service.

It also acknowledges that ownership of the island has been long under dispute, with both the United States and Canada claiming sovereignty.

In Senate order papers to be discussed on Tuesday, Senator Quinn asked Canada’s Department of Fisheries and Oceans, which he says is the administrator of the land, why it issues a permit to an American company “that actively describes Machias Seal Island as part of the state of Maine”.

He also asked why the company is listed on the government website “given Canada’s sovereignty over the New Brunswick Island”.

The US considers Machias Seal Island its territory.

The BBC has contacted both the Canadian government and Bold Coast Charter Company for comment.

The island is the only land disputed by Canada and the US, though an international court ruling in 1984 gave both countries the right to fish in its waterway. Both Americans and Canadians have operated on and around the island since, though the US has long accused Canada of unfair trade action in the local lobster fishery.

President Donald Trump’s decision to implement tariffs, including on Canada, to help boost investment and manufacturing in the US, and past comments about Canada as the “51st state” has caused wider friction between the two countries.

It is because of these comments that Senator Quinn believes Canada should assert its sovereignty over Machias Seal Island and ask that Bold Coast recognise it.

“That’s unacceptable in this day and age, especially with where we are with our neighbours to the south,” he told local news outlet Global.

“We’re being pushed in so many ways, and yet here’s a porous point in our border that nobody’s paying attention to,” Senator Quinn said.