Signs of a split between Nigel Farage and a key ally have been laid bare after Arron Banks urged Tory MPs to back Boris Johnson’s Brexit deal even though the former Ukip leader thinks that it amounts to “vassalage”.

Mr Banks, who campaigned alongside Mr Farage under the Leave.EU banner, contacted MPs last week before Saturday’s vote in parliament.

He encouraged the 28 Spartan Tory MPs, who held out three times against Theresa May’s Brexit plans, to vote for the prime minister’s proposals.

Mr Banks is understood to support Mr Johnson’s deal in the belief that it is better to get an imperfect agreement over the line than for the UK to stay in the EU for much longer.

However, Mr Farage, leader of