The manufacture of lithium in China is referred to as “slave labor” by Justin Trudeau, the prime minister of Canada, who was speaking about his nation’s efforts to increase production of the metal used in batteries for electric vehicles and other devices.

However, over the years, China has made strategic decisions that have made it the world’s largest producer despite the fact that Canada has sizable lithium reserves, according to Trudeau.

“If we’re honest … the lithium produced in Canada is going to be more expensive. Because we don’t use slave labor,” Trudeau said in remarks at the Council on Foreign Relations in New York.

“Because we put forward environmental responsibility as something we actually expect to be abided by. Because we count on working with, in partnership, with Indigenous peoples, paying their living wages, expecting security and safety standards.”

A representative for the Chinese Embassy in Ottawa did not respond to a request for comment.

Canada last year announced a tougher policy on critical mineral investment – particularly from China – as it worked to shore up its domestic supply after the global pandemic exposed supply chain problems.

“If the pandemic taught us anything, if the pandemic taught us anything, it’s resilience, redundancy and reliability in our supply chains,” Trudeau said.

The United States has alleged use of forced labor by China in sectors including mining and construction. Last year, a U.S. law took effect banning imports from China’s Xinjiang region over concerns about forced labor.

In December, the United Auto Workers union called on automakers to shift their entire supply chain out of Xinjiang after a report by Britain’s Sheffield Hallam University suggested that nearly every major automaker has significant exposure to products made with forced labor.

China denies abuses in Xinjiang, a major cotton producer that also supplies much of the world’s materials for solar panels.

Chinese firms also own, operate or finance most of the Democratic Republic of Congo’s cobalt mines, the U.S. Labor Department said in a recent report. “Our research shows that lithium-ion batteries are produced with an input – cobalt – made by child labor,” it said.

Diplomatic tensions between Canada and China have been running high since the detention of Huawei Technologies executive Meng Wanzhou in 2018 and Beijing’s subsequent arrest of two Canadians on spying charges.

In November, Canada ordered three Chinese companies to divest from Canadian critical minerals, citing national security. China in response accused Ottawa of using national security as a pretext and said the divestment order broke international commerce and market rules.