Royal Bank of Scotland said if Scots vote for independence it would probably "significantly" hit its credit ratings. A rise in credit ratings typically increases a company's funding costs.

"A vote in favor of Scottish independence would be likely to significantly impact the group's credit ratings and could also impact the fiscal, monetary, legal and regulatory landscape to which the group is subject," RBS said in the risk section of its annual results.

Scotland will vote on independence from the UK in September.

RBS CEO Ross McEwan earlier on Thursday said the bank had to makes plans around what the implications of a "yes" vote could be, but added: "This is a huge issue for Scotland and we are neutral and won't do anything to raise the temperature of that vote."

(Reporting by Steve Slater. Editing by Carmel Crimmins)