"The immediate impact ... is to prolong the uncertainty about the future direction of Brexit," Moody's analyst Colin Ellis said in a note to clients.
"The risk of a disorderly no-deal Brexit in particular remains high, and such an outcome would have significant negative credit consequences for a range of issuers," he added.
Last week, Moody's said a no-deal Brexit would represent a profound failure of Britain's political institutions.
(Reporting by David Milliken; editing by Stephen Addison)