The Chancellor is joining other European finance ministers in expressing concerns about the US President’s plans.
Philip Hammond has risked a new row between Theresa May and Donald Trump by attacking the President’s planned tax cuts.
In a highly-provocative move, the Chancellor has teamed up with four other European finance ministers to claim US tax cuts could start a trade war.
Along with his counterparts in France, Germany, Italy and Spain, Mr Hammond has put his name to a hard-hitting letter to US Treasury Secretary Steven Mnuchin.
In the letter, which runs to three pages, the five European ministers express their “significant concerns” about the President’s tax changes “having a major distortive impact on international trade”.
They also claim Mr Trump’s proposed changes could contravene World Trade Organisation (WTO) rules and America’s own tax guidelines.
Mr Hammond’s decision to sign the letter will be seen as hugely controversial, since it risks angering the President at a time when the UK is trying to strengthen its post-Brexit trade links with the US.
The fact that the pro-Remain Chancellor has joined forces with colleagues from leading EU countries to attack tax cuts is also likely to infuriate right-wing Eurosceptic Tory MPs who already want him sacked.