Donald Trump’s administration is warning Britain that it will not get a free trade deal unless a new tax affecting US tech giants is dropped, The Telegraph can reveal.

US officials are demanding that the so-called digital services tax, affecting the likes of Amazon, Google, Facebook and Twitter, is ditched before it becomes law in the autumn.

The threat has been communicated to the UK Government “at multiple levels” and has emerged as one of the most significant hurdles to Boris Johnson’s hopes of a speedy agreement.

Key members of the US Congress, which needs to approve any deal, have also echoed the warning, going a step further to suggest it could even block formal talks from starting.

“The message was, ‘If you go ahead and introduce this tax, we will not begin free trade negotiations with you,’” said one source familiar with the exchange.

The 2 per cent tax on all UK revenues of search engines, social media platforms and online marketplaces was announced by Philip Hammond, the former chancellor, in his October 2018 budget. It is due to be written into law in the autumn 2019 budget and come into effect from April 2020.

It is estimated that the tax will raise more than £400 million for the UK Treasury by 2022. There has been public outcry at the small amounts of tax the likes of Google have paid in Britain. Sources close to Sajid Javid, the new Chancellor, said he was yet to announce his public position on the issue, which is seen by the Trump administration as a “tax grab” on American companies.