The German Chambers of Commerce and Industry has said it is “astonished” that the UK is considering leaving the EU, and that an exit would be “disastrous” for both countries.
Volker Treier, deputy chief executive of the group, said scores of German firms could easily end up taking back investment from the UK. The 400,000 people employed by German companies in Britain are among those who would be negatively affected by such a change.
"We are really astonished about this referendum," he told the BBC. He added that German chancellor Angela Merkel, who Prime Minister David Cameron is meeting in Berlin later today, should not offer any concessions.
There is a risk for the EU that if allowances are made for one country, others will also start demanding negotiations of their membership terms, he said.
The Prime Minister has promised to hold a referendum on membership by the end of 2017, although this could be brought forward to next year. First, however, he hopes to renegotiate Britain's membership terms with the bloc.