Leaving the European Union would cause a decade of uncertainty that could cost Britain's financial services an estimated GBP17 billion ($25 billion) and make lawyers rich, a think-tank study said on Tuesday.

Analysts at JWG, which specialises in managing regulatory changes, takes no position on whether Britain should remain or leave the EU. But it says if Britain votes to leave in June's referendum, financial firms will end up trying to maintain business as usual while making fundamental changes.

"Rather than reduce red tape, UK businesses will be stuck with a rule book that could change by 60 percent, while new court judgements change the rules of the game," the 24-page JWG study of the impact of Brexit said

"The additional cost of Brexit to already bloated UK regulatory change budgets will be GBP17 billion through 2026, not taking into account fines for non-compliance," the study said.

Change would come in three waves: British regulators reshaping rules, EU rules rewired, and from 2022, global rules would be due for revision, it said. Some firms will move quickly to sort out their approach and gain competitive advantage.

"However, the herd will move slowly and consultants, lawyers and technology providers will be the ultimate winners from the next decade," the report said. – Reuters