Donald Trump’s latest plan to slap tariffs on US imports based on sales taxes in their country of origin could shave £16 billion ($20 billion) off UK economic output over the next two years, in what would be a blow to Prime Minister Keir Starmer’s promise to fire up growth.

U.S. President Donald Trump tasked his economics team on Thursday with devising plans for reciprocal tariffs on every country taxing U.S. imports, ramping up prospects for a global trade war with American friends and foes.

I’ve decided for purposes of fairness that I will charge a reciprocal tariff,” Trump said in the Oval Office at the proclamation signing. “It’s fair to all. No other country can complain.”