Lord Adonis has resigned as Theresa May's infrastructure tsar over the Government's approach to Brexit.

The Labour peer stood down from his position as chairman of the National Infrastructure Commission, claiming Mrs May had become the "voice of Ukip" and the "extreme" right-wing of her party.

He said he was "duty bound" to oppose the Government's European Union (Withdrawal) Bill when it comes to the House of Lords.

In his resignation letter, reported by The Sun and The Daily Telegraph, he told the Prime Minister: "Brexit is a dangerous populist and nationalist spasm worthy of Donald Trump.

"After the narrow referendum vote for an undefined proposition to 'leave the EU,' it could have been attempted without rupturing our essential European trade and political relations.

"However, by becoming the voice of UKIP and the extreme nationalist right-wing of your party, you have taken a different course, for which you have no parliamentary or popular mandate."

A National Infrastructure Commission spokeswoman confirmed that Lord Adonis had written to the Prime Minister.