Investors in Europe’s equity and derivatives markets are facing the prospect of higher margin calls from the region’s clearing houses, which are readying themselves for shocks if the UK votes to leave the EU on June 23.

People familiar with meetings taking place among Europe's largest equity clearers - also known as central counterparties, or CCPs - say discussions have focused on the need for common procedures if higher-than-normal margins are required in the event of a so-called Brexit.