HSBC will move 1,000 jobs from London to Paris if the UK leaves the European single market as part of its withdrawal from the European Union.
The banking giant said positions moved would be those that already process payments in euros.
HSBC is the second major employer in the UK to confirm to would move jobs away from the country following the outcome of last week's referendum. On Friday, US banking giant Morgan Stanley said it could confirm 2,000 jobs from London to Dublin or Frankfurt.
Various economists and European leaders have warned that finance firms want unrestricted access to the EU, which is likely to hurt London's position as Europe's financial centre.
Financial lobby group TheCityUK said it was focused on ensuring the UK remains part of the single market.
Just a few months ago, HSBC announced a decision to keep its headquarters in London. The bank had considered a move away after the government imposed a string of tighter rules and regulations on the banking sector.
