German businesses operating in the UK have voiced concern at the prospect of Britain leaving the European Union.
Trade body German Industry UK backed David Cameron's drive to achieve reform of the EU, but urged the Prime Minister to give a "firm commitment" to keep Britain in if he achieves his goals.
Following the general election in May, the PM kicked off a process of renegotiation of UK membership which will lead to an in/out referendum by the end of 2017.
GIUK's warning against Brexit was based on a survey of 90 German companies operating in Britain, with a combined workforce of 220,000 in the UK and more than four million globally.
In their statement, they said: " The UK is one of Germany's most important markets worldwide and the EU the main market for the UK.
"German business in the UK strongly agrees with Prime Minister David Cameron that there must be significant reductions in EU costs, bureaucracy and regulations.
"Nevertheless, we, as much as British business, are concerned at the prospect of a UK outside the EU which could be the outcome of an in/out referendum.
"After he achieves the necessary reforms we would urge the Prime Minister to convince the British people of the financial, economic and social benefits of the EU for the UK and give a firm commitment to remain in the EU."
GUIK chairman and chief executive Bernd Atenstaedt said: "We respect the decision made by the Prime Minister to hold a referendum and the people's decision in the referendum, but believe it is in the UK's best interest to stay in the EU for the benefit of our employees and ultimately, the general public".