Conservative Leader Andrew Scheer is urging Prime Minister Justin Trudeau to step up inspections on all products from China and to consider slapping tariffs on imports from the Asian country.

In a letter Friday, Scheer pressed Trudeau to take a harder line with Canada’s second-biggest trading partner at a time when the countries are locked in a diplomatic dispute that has dragged on for more than seven months.

China detained two Canadians in December just days after Canada arrested Chinese high-tech executive Meng Wanzhou in Vancouver on a U.S. extradition warrant.

Angered by Meng’s arrest, China has increased inspections that have led to the suspension or obstruction of key Canadian agricultural imports, including pork and canola.

Last week, China announced an additional suspension of all imports of Canadian meat products because of claimed concerns over fraudulent inspection reports.

Scheer wants Trudeau to respond by intensifying Canadian inspections on all imports from China and to start exploring possible retaliatory levies on Chinese products that will have the greatest possible impact while minimizing harm to consumers in Canada.

Trudeau has tried to get China to release the detained Canadians by encouraging to allies to tell Beijing it needs to follow the rule of law and other international standards.

The prime minister and Kelly Craft, the U.S. ambassador to Canada, have said President Donald Trump raised the plight of Michael Kovrig and Michael Spavor with President Xi Jinping during the recent G20 summit.

Scheer says Canada must do more to secure the release of the former diplomat and the entrepreneur, who were both arrested on allegations of undermining China’s national security.

“There is no other way to put this: Canada is being bullied by the Chinese government and you have done nothing to stand up for Canada in response,” Scheer wrote in the letter to Trudeau.

He added that Canada imported more than $75 billion worth of goods from China last year.

“In short, we have leverage in this dispute, but only if we choose to wield it.”

Scheer also reiterated his calls for Trudeau to launch a complaint against China with the World Trade Organization and to cut Canadian funding to Beijing’s Asian Infrastructure Investment Bank, to which the Liberal government has committed $256 million over five years.