LONDON (AP) — The CEO of the London Stock Exchange has offered a dire warning on the risks associated with the uncertainty of Brexit, with thousands of jobs in the balance, particularly from the lucrative business of clearing contracts.

Xavier Rolet warned lawmakers Tuesday that Brexit would potentially have a systemic impact and that many jobs associated with clearing of financial trades were at risk.

He said: "I'm not just talking about the clearing jobs themselves which number into the few thousands, but the very large array of ancillary functions... which range into far more than just a few thousand or tens of thousands of jobs."

He says Britain's financial services sector needs a grandfathering period of five years to "maintain, nurture and promote" what has made the U.K. economy a global performer.