EU will 'never, never, never' compromise on single market - Barnier

The European Union's chief Brexit negotiator on Monday warned Britain that the bloc would "never, never, never" compromise on the integrity of its single market, adding London had underestimated the costs of leaving.

Some British politicians have suggested that Brussels might be flexible on its rules in order to protect trade flows, but Michel Barnier told an audience in Belfast the single market was the bloc's most valuable asset and would not be compromised.

(This story is refiled to add Barnier's first name)

(Reporting by Amanda Ferguson; Writing by Conor Humphries; Editing by Chris Reese)