President Donald Trump has hiked temporary tariffs on US imports from all countries from 10% to 15%, hours after the US Supreme Court declared his use of emergency tariffs a “disgrace to the nation”.

In a post on social media platform Truth Social, Trump wrote: “I, as President of the United States of America, will be, effective immediately, raising the 10% Worldwide Tariff on Countries, many of which have been ‘ripping’ the U.S. off for decades, without retribution (until I came along!), to the fully allowed, and legally tested, 15% level.”

It follows the US court’s ruling on Friday, which decided the president needed congressional approval for his use of the International Emergency Economic Powers Act (IEEPA), which saw Trump last year hike global tariffs.

It is understood that US law allows the president to implement levies of up to 15% for 150 days, but requires congressional approval for anything longer than that time-period.

It is not yet clear when the 15% tariffs will take effect. However, the White House has confirmed that the original 10% levy will come into force at 5:01am in the UK on 24 February (12:01am Eastern Time on Tuesday, 24 February).

While Trump said the new tariffs would take effect “immediately”, it is not confirmed exactly when the 15% tariffs will be introduced.

British Chambers of Commerce head of trade policy William Bain said the president’s decision to raise tariffs would be “bad for trade”.

“The 40,000 UK companies exporting goods to the US will be dismayed at this latest turn of events. We had feared that the President’s Plan B response could be worse for British businesses and so it is proving,” he said.

“This means an extra 5% increase in tariffs on a wide range of UK goods exports to the US, except those covered under the Economic Prosperity Deal. This will raise the tariff cost on UK exports to the US by between £2bn and £3bn.

“This will be bad for trade, bad for US consumers and businesses and weaken global economic growth. Businesses on both sides of the Atlantic need a period of clarity and certainty. Higher tariffs are not the way to achieve that.”

However, Bain added: “The one ray of light in this new scenario is that this 15 per cent tariff will need to be approved by Congress after 150 days. It is now vital that the government and business continue dialogue with their US counterparts to retain the UK’s competitive advantage and reduce tariffs as far as possible.”

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