LONDON (Reuters) - Britain's Sunday Times newspaper called on its readers to vote to leave the European Union in Thursday's referendum as a way to press for deeper reform of the bloc, which might make it more acceptable for Britain to actually remain in.

"Yes, we must be prepared for a bumpy ride, but we should hold our nerve. This vote may be the only opportunity we shall ever have to call a halt to the onward march of the centralizing European project," the newspaper said in an editorial.

The newspaper said it supported the idea floated by leading "Out" campaigner Boris Johnson of Britain holding a second referendum after negotiations on further reform with Brussels.

(Writing by William Schomberg; Editing by Cynthia Osterman)