Arron Banks has apologised for a Leave.EU tweet that called German chancellor Angela Merkel a 'kraut'.
The co-founder of the pro-Brexit group said the meme, which was posted on Twitter following news of a phone call between Ms Merkel and prime minister Boris Johnson, had gone "too far".
The post showed a photo of Ms Merkel with the words: "We didn’t win two world wars to be pushed around by a Kraut".
It was accompanied with the caption: "Angela Merkel’s demand that Britain leaves Northern Ireland to rot inside the customs union is reprehensible and shows the true colours of our supposed ‘European allies’.”
It came following the news that Ms Merkel had reportedly told Mr Johnson that a Brexit deal which took Northern Ireland out of the customs union was "essentially impossible".
The image was condemned by cross-party MPs and later deleted.
Good Morning Britain host Piers Morgan branded the tweet as "xenophobic nonsense" and told the Leave.EU group: "You don't speak for Britain".
After being called out for a Daily Mirror front page with the headline "Achtung! Surrender!" which was published during the Euro '96 football tournament while Mr Morgan was editor, the breakfast show host said: "Your meme isn’t meant as a joke, is grotesquely offensive, and makes you guys look like racist idiots."
Mr Banks, who had initially defended the meme, later said the tweet was "unauthorised" and the point "could have been made better".
He claimed "the sentiment holds true" but "the team went too far".
