Influential peer Lord Adonis has quit his post as an infrastructure adviser, saying that the government has become too aligned with Ukip over Brexit.
Adonis was head of the government's National Infrastructure Commission (NIC), but has told Theresa May that Brexit is preoccupying Whitehall, and that she is not focused on other political issues.
The peer has chaired the NIC since 2015, and served as transport secretary for Gordon Brown between 2009 and 2010.
In his resignation letter, Adonis said: "Brexit is a populist and nationalist spasm worthy of Donald Trump. After the narrow referendum vote, a form of associate membership of the EU might have been attempted without rupturing Britain's key trading and political alliances.
"Instead, by allying with UKIP and the Tory hard right to wrench Britain out of the key economic and political institutions of modern Europe, you are pursuing a course fraught with danger."
He said that future generations will seek to bring the UK back into the EU.
Former chancellor George Osborne tweeted to thank Adonis for his work, and said that the next appointee must be bipartisan.
I appointed Andrew in 2015 because I also wanted our new National Infrastructure Commission to have the bipartisan authority to generate a national consensus over long term thinking - the key thing UK infra plans lack. It’s vital that’s sustained if NIC is to make lasting impact— George Osborne (@George_Osborne) December 29, 2017
Liberal Democrat leader Vince Cable said: "Lord Adonis is one of the most thoughtful politicians around. This is why he has so many friends and political admirers beyond the Labour Party.
"It is, then, a great shame that he is no longer leading Britain's infrastructure programme."