The warning was issued by the former French ambassador to the UK, Sylvie Bermann, when Mr Johnson came to deliver a speech at the French Embassy in London. Mr Johnson was at the time the newly appointed Foreign Secretary and gave his talk almost a month after leading Vote Leave to their stunning victory in the Brexit referendum. The Foreign Secretary was booed by British members of the audience as he delivered his upbeat message about the future.
In an interview with the New European, Ms Bermann recalled: “I was embarrassed as he was my guest and so I made a point of accompanying him to his car when he left shortly afterwards.
“He was saying they were only a few Remainers and I wasn’t to worry as everything was going to be alright.
“I told him things were actually going to get very difficult for the UK and he needed to understand that.
She accuses the Prime Minister and Michael Gove of having exploited negative attitudes to immigration to secure their Brexit triumph.
Mr Johnson has consistently delivered an upbeat message on Brexit, arguing that it creates new opportunities for economic growth and prosperity.
He has also argued that leaving the EU would enable the Government finally to focus on the “people’s priorities”, such as the NHS.