LONDON/ZURICH (Reuters) - Swiss bank UBS UBSG.S asked staff whether they would prefer to relocate to Amsterdam, Madrid or Frankfurt after Britain leaves the European Union in a survey sent to its investment bankers on Tuesday, according to sources familiar with the matter.

FILE PHOTO: The offices of Swiss bank UBS are seen in the financial district of the City of London, Britain October 31, 2012. REUTERS/Chris Helgren/File Photo

Financial service firms need a regulated subsidiary in an EU country to offer products across the bloc, which means some are looking to move jobs out of Britain if it loses access to the European single market.

The Swiss bank said in July it was weighing up whether to move some jobs in London to Frankfurt, Madrid or Amsterdam.

The bank has estimated that it would need to move around 1,000 people from London to the EU to retain full ‘passporting’ rights to sell products and services across the bloc, which would equate to around a quarter of its 5,500 staff currently based in the British capital.

In its voluntary survey of staff sent out on Tuesday the questions asked included: “state your first, second and third choice between Amsterdam, Madrid and Frankfurt on where you’d prefer to relocate after Brexit”.

A spokesman for UBS in London declined to comment on the survey.

Whilst most of the Wall Street banks have now chosen where to base their EU headquarters, UBS is amongst the last of the big banks to decide on a location.

Investment banking boss Andrea Orcel told a conference in September that the preference of staff would be the biggest factor for UBS.

He said by trying to understand where people prefer to move, UBS should be able to reduce employee attrition and the costs of hiring and training, and keep staff happier.

“The key issues are going to be residential and schooling,” he said. “That will be a challenge for any location,” he said.

The world’s biggest wealth manager has also set up a bank in Frankfurt to consolidate most of its European wealth management operations.