The president of Europe’s meeting of finance ministers says a hard Brexit will blast the UK back to the 1970s, becoming a "pariah" with "enormous unemployment, and total deterioration".
When finance ministers of euro-using countries get together they are known as the Eurogroup.
The Eurogroup’s president, Dutch finance minister Jeroen Dijsselbloem, launched an uncompromising attack on the "Hard Brexit" speech that Prime Minister Theresa May gave at London’s Lancaster House this week.
Mr Dijsselbloem made the remarks at the World Economic Forum in the Swiss mountain resort of Davos.
He warned that under Mrs May’s plan England would "deteriorate" and "be back where it was in the 1970s".
He said: "In 20 years, England will be back where it was in the 1970s. Totally obsolete, enormous unemployment and total deterioration. It does not seem the model to me for a future for England."
He did not mention Wales, Scotland or Northern Ireland but his comments were taken to mean all of the UK.
Dijsselbloem made the remarks after Theresa May said in her recent speech she wants a full and hard Brexit, with the UK also exiting the internal European market.
He added: "She threatens to become a sort of pariah on the edge of Europe, a tax paradise. That is exactly the direction we should not want to go."
The Labour party politician also criticised Trump's isolationism, but said he saw some positive signs in the incoming US President’s protectionist rhetoric.
He said: "That Trump calls on big businesses to take responsibility...I am very sympathetic to that."
Dijsselbloem is perhaps best known because of his frequent head-on clashes with former Greek finance minister Yanis Varoufakis.
According to European Commissioner Pierre Moscovici the two even almost came to fisticuffs in a meeting in February 2015 about the Greek euro crisis.
Varoufakis later called Dijsselbloem "intellectually lightweight", "untrustworthy" and a "liar".