LONDON (AP) — The European Union is moving ahead with new rules that could force a key financial market to leave London once Britain exits the bloc.

The European Commission, the EU's executive body, proposed Tuesday to tighten its oversight of companies that clear euro-denominated derivatives, a market currently dominated by U.K.-based firms. The draft regulations would force any firm considered important to the EU financial system to accept direct oversight from the bloc and, if requested, relocate to within the EU.

The move affects tens of thousands of jobs in Britain, where three-fourths of euro-denominated interest rate derivatives are cleared.

Commission Vice President Valdis Dombrovskis said the EU "needed to make certain adjustments to our rules to ensure that our efforts remain on track."