Republicans on Capitol Hill have largely fallen in line with Donald Trump’s move to impose tariffs on the US’s biggest trading partners, with the notable exception of the former Senate majority leader Mitch McConnell, who called it a “bad idea”.

With even Trump admitting that the tariffs – 25% on imports from Canada and Mexico and 10% on China – might cause “some pain”, there was mostly strong support from the president’s loyalists. Jason Smith, chair of the ways and means committee of the House of Representatives, said the tariffs would “send a powerful message that the United States will no longer stand by as other nations fail to halt the flow of illegal drugs and immigrants into our country”.

He added: “On top of these crises, our neighbours continue to take advantage of American workers, manufacturers, and farmers, including Canada’s refusal to allow real access to its dairy market and Mexico’s unjustified barriers to US corn.”

Byron Donalds, a Republican representative from Florida, said risks that the tariffs would fuel inflation – a key concern among voters that contributed to Trump’s election victory – were “worth it”.

Eric Schmitt, a Republican senator from Missouri, also told NBC’s Meet the Press that they “are meant to bring Canada and Mexico to the table for the fentanyl that is streaming into our communities”.

That rationale was dismissed by Chrystia Freeland, the former Canadian finance minister who is running for the leadership of the governing Liberal party. Freeland told MSNBC’s Morning Joe programme that the Canadian border accounted for just 0.2% of fentanyl entering the US and that the issue could be solved “in five minutes”.

Another Trump ally, the South Carolina senator Lindsey Graham, offered more qualified support, telling Fox News: “I think the tariffs probably go away” if they succeed in getting “these countries to change their behaviour”.

The Tax Foundation, a non-partisan thinktank, has estimated that the tariffs would be equal to an $830 tax increase on the average household.

One of the few exceptions to the chorus of support for Trump’s trade war was McConnell, who has often clashed with the president. “It will drive the cost of everything up. In other words, it will be paid for by American consumers. I mean, why would you want to get into a fight with your allies over this?” he told CBS’s 60 Minutes programme.

Two other Republican senators, Susan Collins of Maine and Rand Paul of Kentucky, have voiced doubts, with Paul calling tariffs “simply taxes”.

• Trump administration
• Donald Trump
• US politics
• Mitch McConnell
• Republicans
• Mexico
• Canada
• news