(Drops extraneous "and" in paragraph eight)
LONDON, Sept 18 (Reuters) - Around 10,000 finance jobs will be shifted out of Britain or created overseas in the next few years if the UK is denied access to Europe's single market, according to a Reuters survey of firms employing the bulk of workers in international finance.
Reuters approached 158 banks, asset managers, private equity firms, insurers and exchanges with UK operations on their plans for moving staff as a result of Brexit and received answers from 123.
Fifty-seven companies said they would have to move staff or restructure their businesses because of Brexit, which is due to take place in March 2019.
Another 37 said Brexit would have no impact, and the remainder said they are still deciding what to do or declined to comment.
The survey was conducted by email and telephone interviews between Aug. 21 and Sept. 15. A total of 55 banks responded, along with 37 insurers and insurance brokers, 28 asset managers and private equity firms, and three exchanges.
They included the 20 investment banks that earned the most fees from investment banking in Europe, the Middle East and Africa in 2016, according to Thomson Reuters' data.
Some participants declined to comment on some of the questions. Some participants also asked for the information to be part of an aggregate only, which is why Reuters has not published the complete data.
The insurers who responded to the survey included the largest listed insurers in Britain, along with large European Union and non-EU insurers operating in Britain, major insurance brokers and listed and unlisted insurers with an international focus, such as those operating in the Lloyd's of London market.
Twenty-eight asset managers managing a collective $25 trillion responded. They included most of the global managers who use the UK as a base in Europe, as well as the leading British firms.
Survey participants were asked if Brexit would mean new jobs in the European Union and if so, to give details about whether they would be new jobs or transfers from London. They were also asked how many UK employees they currently have.
Seventy-five organisations provided the number of staff they currently employ in the UK, which added together totalled 484,578. Of those 357,617 were employed by banks, 106,348 by insurers, 16,363 by asset managers and 4,250 by exchanges.
The 39 firms which gave details on their plans for Brexit staffing together employ at least 359,983 people. A precise number could not be calculated because four did not answer the question.
The 20 banks in the survey who answered the question about how many jobs would be affected by Brexit said they expected 9,777 jobs to be moved or created in the EU.
Eleven insurers expected 98 roles to be created in the EU in total. Eight asset managers and private equity firms who gave the information saw 311 jobs in total being created.
Of banks who have made a decision on what to do about Brexit, six planned to add jobs in Frankfurt, four in Paris, three in Dublin, two in Amsterdam, one in Berlin and one in Brussels.
Among insurers, seven were setting up subsidiaries in Luxembourg, six in Dublin, three in Brussels, and one each in Malta, Munich and Paris.
For the asset managers, nine said they were considering moving staff to another country or hiring locally there. The most popular destination was Luxembourg, chosen by seven firms, followed by Dublin with one and one undecided.
There are 344 banks registered in Britain, according to the Bank of England, although that includes the domestic-focused subsidiaries of many larger banks as well as many smaller lenders that earn the bulk of their revenue in Britain so won't be affected so much by Brexit.
There are 503 UK authorised insurers, according to the Bank of England, though many larger firms have more than one authorisation. Many UK insurers also have a purely domestic focus, insurance specialists say.
While the asset managers contacted account for the lion's share of the assets managed in Britain, there remains a long tail of smaller managers registered with the Financial Conduct Authority, a figure it currently puts at 1,840 firms. (Compiled by Carolyn Cohn, Andrew MacAskill, Noor Zainab Hussain, Simon Jessop and Dasha Afanasieva; Editing by Sonya Hepinstall)