In January the government imposed an extra 8 percent tax on bank profits above 25 million pounds ($30.8 million) to run concurrently with an additional levy on their balance sheets.

"Banks are firmly committed to paying our fair share but we are now at a tipping point that threatens UK jobs and growth," Anthony Browne, chief executive of the BBA, the UK's largest bank lobby group, will tell a conference on Thursday.

"It is essential that the UK remains a competitive place to do business for international banks," he added in remarks released ahead of his speech.

Bankers have warned they will have to start moving operations out of London as early as next year if Britain loses access to the European Union single market. [nL8N1CI0N9]

Britain could safeguard London as a top banking centre by scrapping the levy on bank's balance sheets and surcharge on profits, or drastically reducing both if this was not politically possible, think-tank Open Europe said in a report earlier this week.

($1 = 0.8130 pounds)

(Reporting by Andrew MacAskill; Editing by Keith Weir)