Britain's business on the first day of the UK settlement cut off could cause tur

Sally Dewar, head of international regulatory oversight at JPMorgan JPM, said on Wednesday that the financial markets would be in turmoil on the day the Brexit was put off if European clearing houses' UK client businesses were suddenly cut off.

Dewar said that if the EU did not recognize the UK's clearing agency before the EU's March 2019 Brexit, the market would be seriously hampered.

"Without recognition, the first day of Brexit could lead to market turmoil, so we can not expect the level of impact," Dewar said to a committee of the British House of Lords.