Boris Johnson will find Brexit negotiations with the EU even tougher than Theresa May did if he becomes prime minister, officials in Brussels warned.

Senior EU officials and diplomats note that throughout the Brexit turmoil of the past two years Mrs May was “never given the cold shoulder”.

“The question was always, ‘What can we do to help?’ ” said one European ambassador. “That will not be case for a new prime minister when the favourite candidate has a big trust deficit with us.”

In Brussels Mr Johnson is viewed as the frontrunner, followed by Jeremy Hunt, the foreign secretary, and Michael Gove, the environment secretary. Matt Hancock, the health secretary, and Sajid Javid, the home secretary, are serious contenders who are not viewed as