Britain will not get its free trade deal with America passed in the US Congress if Brexit undermines the Good Friday Agreement, the most senior Democrat in the House of Representatives has said.

Nancy Pelosi released a statement on Wednesday reiterating that there will be “no chance” of a deal getting the congressional approval it needs unless the Irish border remains “seamless”.

The warning carries bite given that Ms Pelosi’s party, the opponents of Donald Trump’s Republican Party, holds the majority in the House.

Both the House and the Senate, the two chambers of the US Congress, must vote through any deal struck between Britain and America for it to come into effect.

The intervention, which underlines a position Ms Pelosi made clear in public earlier this year, comes after a trip to Britain by John Bolton, the White House national security adviser.

During the visit Mr Bolton repeatedly talked up the prospect of a deal, floating the idea of smaller sector-by-sector agreements that could be struck rather than a single all-encompassing one.