LONDON - Britain is more likely to leave the European Union without a deal after Boris Johnson was chosen to succeed British Prime Minister Theresa May on Tuesday, credit ratings agency Moody's said.

Johnson has pledged to deliver Brexit on Oct. 31 even if it means leaving without a deal. He defeated Jeremy Hunt in a ballot of party members to become the new Conservative party leader and will be appointed as PM on Wednesday.

"With the election of Mr Johnson, the likelihood of a sustainable compromise appears lower than before," said Colin Ellis, Moody's Managing Director for Credit Strategy.

"Our view remains that a no-deal Brexit would have significantly negative credit effects for the UK sovereign and related issuers."

(Reporting by Alistair Smout; editing by Stephen Addison) ((alistair.smout@thomsonreuters.com; +44 207 542 7064; Reuters Messaging: alistair.smout.thomsonreuters.com@reuters.net))