The European Council President has called Foreign Secretary Jeremy Hunt’s comparison of the EU and Soviet Union as “unwise”.
Donald Tusk demanded greater respect from the UK government, saying “unacceptable comments” were achieving nothing other than causing tension in the Brexit negotiations.
Mr Tusk also rejected any suggestion that the EU had not respected the dignity of the UK at the recent meeting of European leaders at Salzburg.
'Not my problem'
European Council President Donald Tusk shakes hands with Ireland's Prime Minister Leo Varadkar in Brussels
The European Council President referenced Mr Hunt’s comments after a meeting with Irish leader Leo Varadkar in Brussels.
He said: "In respecting our partners, we expect the same in return.
"Comparing the EU to the Soviet Union is as unwise as it is insulting.
"The Soviet Union was about prisons and gulags, borders and walls, violence against citizens and neighbours.
"The European Union is about freedom and human rights, prosperity and peace, life without fear, it is about democracy and pluralism - a continent without internal borders and walls.
"As the President of the European Council and someone who spent half his life in the Soviet bloc, I know what I am talking about."
The EU council president added: "Unacceptable remarks that raise the temperature will achieve nothing except wasting more time."
Asked if Mr Hunt should resign over his comments at the Conservative Party conference, Mr Tusk replied: "That's not my problem".
'We should get down to business'
Foreign Secretary Jeremy Hunt giving his speech at Conservative Party Conference in Birmingham
The key EU figure did however suggest that the Tory conference had served as a distraction to the negotiations.
He said: "I was party leader myself for 15 years and I know what the rules of party politics are.
"But now the Tory Party Conference is over we should get down to business."
Mr Tusk also referenced the less comprehensive Canada-style trading deal as advocated by Brexiteers like Boris Johnson and David Davis.
He said the EU was offering a "Canada plus, plus, plus deal", stressing the European desire for as close a relationship as possible with the UK after Brexit.
Mrs May has insisted her Chequers blueprint is the only proposal that would honour the referendum vote to leave the EU while avoiding the return of a hard border between Northern Ireland and the Republic.