A potential U.K. exit from the European Union could cause 4,000 Britain-based J.P. Morgan employees to lose their jobs.
That’s according to the investment banking giant’s CEO, Jamie Dimon, who spoke to his Bournemouth, U.K. staff Friday.
“It is my opinion that it is a terrible deal for the British economy and jobs,” Dimon said in a video obtained by Bloomberg. The bank currently employs over 16,000 workers across the country. “I don’t know if that means a thousand jobs, 2,000 jobs, it could be as many as 4,000, and it would be both jobs all around the U.K.”
The E.U. has a set of guidelines called the “passport” rules, which allow a financial institution to set up shop in one country and serve the rest of the union without further authorization from other member states. The rules also allow the banks to operate from one country and serve another without setting up local operations in the latter. But in the case of a Brexit, the banking industry would likely have to wrestle with two sets of regulations and spread out operations throughout the continent—ramping up expenses.
“One realistic outcome is that we lose the ability to passport our banking and trading services into Europe. But our clients will still need us to trade within what will then be the EU. If that’s what the rules say, we will need to do what works,” Dimon said in a set of prepared remarks provided to Fortune by J.P. Morgan. “So if the UK leaves the EU, we may have no choice but to re-organize our business model here. Brexit could mean fewer J.P. Morgan jobs in the U.K. and more jobs in Europe.”
It’s not just J.P. Morgan that would have to overhaul its operations in Europe in the case of a Brexit.
Goldman Sachs has taken heavy advantage of the passport rules, with 6,000 of its 6,500 of its European employees based out of the U.K. The bank is also building a London headquarters, set to open 2019. HSBC has flagged the possibility of moving 1,000 U.K. jobs to Paris, according to Reuters. Deutsche Bank has warned that it could move large chunks of operations from the U.K. to Germany, according to the Financial Times. Banks are also preparing for a potential Brexit by looking toward Dublin as their new home base.
“I cannot, and will not, tell the British people how to vote on this,” Dimon said during the talk Friday. “But when you vote, you should be thinking about something like that.”
The U.K. is set to vote on the referendum June 23.