British and German business groups have issued a plea to politicians to put economic interests first as they enter the third round of Brexit talks.
The British Chambers of Commerce (BCC) and the Association of German Chambers of Commerce (DIHK) have demanded certainty on "business-critical" areas such as custom arrangements, tax and workers' rights.
The organisations said business was deteriorating for German firms trading with the UK because of Brexit uncertainty, while British companies want a transition period of at least three years to cope with the divorce.
Adam Marshall, director general of the BCC, said: "As Brexit talks continue, it's clear that companies in the UK and on the continent all want economic issues to rise to the top of the negotiations agenda.
"There is real business appetite from both sides for a focus on practical, day-to-day business concerns, and a desire for clarity on future trading arrangements.
"The UK and the EU must begin work on transitional arrangements, particularly on customs, so that firms on both sides of the Channel have the confidence to make investment decisions.
"Chambers of commerce in the UK and in Germany want to see thriving trade continue between our firms, both now and into the future. Politicians must do everything in their power to help this happen."
Britain enjoys strong economic ties with Germany.
The UK is the third largest market for the export of German goods, while Germany is Britain's second biggest market for exports of goods and services.
Martin Wansleben, chief executive of the DIHK, said: "Businesses are very concerned that Brexit will have a major negative impact.
"Not only it could lead to more trade barriers - additional bureaucracy, increased waiting time and stricter border controls resulting in higher costs.
"The terms of exit are still completely unclear. Many of our members are reporting that they are already shifting investments away from the UK in anticipation of these barriers.
"The first effects of the Brexit vote are already being observed: German exports to the United Kingdom were down by 3% in the first half of this year compared to the first half of last year, whilst exports to the EU increased with 6% in the same period.
"A transitional period would be helpful for business, but it is important to businesses on both sides that the contours of a future trading relationship are becoming clearer over the next months."
German firms have 2,500 branches in the UK employing 400,000 workers, with British firms holding a smaller 1,200 branch offices and 220,000 staff in Germany.