Britain's new chief Brexit negotiator has warned EU member states not to "underestimate" Boris Johnson in his first contact with his counterparts.
David Frost, the prime minister's new Europe advisor, said EU governments should "be in no doubt" about the new administration's commitment to leaving the EU on 31 October.
"I will save the substantive issues for another day, other than to note prime minister Johnson's statement in parliament [last week], which sets out our approach, and to underline that you should be in no doubt about this government's commitment to the 31 October date," he said in an email to member state diplomats leaked to the Financial Times.
"I would also add that many people are inclined to underestimate Boris Johnson and I would urge you not to do so."
Mr Frost, who replaces Theresa May's Brexit chief Olly Robbins, also hailed his predecessor, who he said "deserved better" than the personal criticism he had received in the press.
"I would like to conclude with a tribute to Olly. It is obvious that this new government does not take the same view as its predecessor on Brexit policy, bu that should not detract from the fact that he has worked tirelessly over the last three years to implement the mandate he was given and has come in for quite a lot of personal criticism as result," he wrote in the email, sent last week.
"He has deserved better, and I know that prime minister Johnson appreciates his service and wishes him well for what comes next."
Mr Robbins came to be disliked by some Brexiteers, who considered the civil servant to be working to frustrate Brexit. Criticism came to a head after he was overheard in a hotel bar in Brussels outlining parts of the government's strategy to get its withdrawal agreement through the House of Commons.
Mr Frost previously worked in Brussels at the UK's Permanent Representation to the EU, and was most recently chief executive of the London chambers of commerce.
Speaking in the Commons last week the new prime minister Mr Johnson said he would not conduct any further Brexit talks with the European Union unless it agreed to drop the controversial Irish border backstop from the withdrawal agreement. The EU has responded by saying it would stand by the policy.
