Labour MP Gisela Stuart, who is from Bavaria and moved to Britain in 1974, was representing the Leave campaign alongside Boris Johnson and Tory minister Andrea Leadsom in a BBC debate in front of 6,000 people at Wembley Arena.
But businessman and Remain backer Lord Sugar took exception at her appearance in the debate, tweeting: “I find it strange that Gisela Gschaider [referring to her maiden name] a 1974 immigrant from Germany is on the Brexit panel telling us British what we should do.”
And former Tory MP Louise Mensch tweeted: “@Lord_Sugar PIG”.
Others piled in to take exception to his tweet, calling it "racist" and "nonsense".
In a series of tweets, he said: “Yes she is (British) now, and has been arguing that we need to curb immigrants from the EU. She immigrated to UK from Germany in 1974.
“30 mins ago was advocating that we stop immigration from the EU like Germany in future and exit EU.”