Keir Starmer is scrambling to stop Donald Trump's latest tariff assault inflicting more damage on the UK economy today.
The US president has escalated his response after the Supreme Court dramatically struck down his 'liberation day' reciprocal levies on Friday.
Mr Trump initially said he would be imposing a new 10 per cent global levy - but then upped that to 15 per cent yesterday.
Businesses warned the move means many will face higher tariffs than before the intervention by the American legal system, as the rate previously applied to the UK was 10 per cent.
British officials hope the changes will not affect preferential arrangements the PM negotiated on steel, cars and pharmaceuticals, but the situation remains unclear.
The US administration is also threatening to step up pressure for the UK to make concessions on chlorinated chicken, pharmaceutical costs and tech firms.
Donald Trump has escalated his response after the Supreme Court dramatically struck down his 'liberation day' reciprocal levies on Friday
William Bain, head of trade policy at the BCC, said: 'We had feared that the President's plan B response could be worse for British businesses and so it is proving.
'This means an extra 5 per cent increase in tariffs on a wide range of UK goods exports to the US, except those covered under the Economic Prosperity Deal.
'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.'
Paul Ashworth, chief North America economist for Oxford Economics, told the Telegraph: 'For the UK that thought it had secured a more advantageous 10 per cent rate this is something of an eff you.'
Mr Trump used 'emergency powers' to introduce the reciprocal tariffs in April, but that was ruled illegal by the Supreme Court.
He has signed a presidential order to reinstate the global levies, but must get approval from Congress within 150 days.
Education Secretary told Sky News' Sunday Morning With Trevor Phillips: 'We, through the work that the Prime Minister has been leading in engaging with the US government and with President Trump, we would hope and expect that to continue, but these discussions are ongoing.
'This is an evolving situation. But of course, we want to get the best possible deal for British businesses.
'I understand the uncertainty it does cause for them, but they can be assured that we will always be working to make sure they get everything that they need.'
The UK Government said it expects Britain's 'privileged trading position with the US' to continue despite the 15 per cent rate.
A spokesman said: 'This is a matter for the US to determine but we will continue to support UK businesses as further details are announced.
'Under any scenario, we expect our privileged trading position with the US to continue and will work with the administration to understand how the ruling will affect tariffs for the UK and the rest of the world.'
Mr Trump used 'emergency powers' to introduce the reciprocal tariffs in April, but that was ruled illegal by the Supreme Court
In his post on Saturday, the US President said: 'Based on a thorough, detailed, and complete review of the ridiculous, poorly written, and extraordinarily anti-American decision on Tariffs issued yesterday, after MANY months of contemplation, by the United States Supreme Court, please let this statement serve to represent that I, as President of the United States of America, will be, effective immediately, raising the 10 per cent 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 per cent level.'
