LONDON (Reuters) - Britain's right-leaning Mail on Sunday newspaper has endorsed the campaign to remain in the European Union, its deputy news editor said on Saturday.

The newspaper, which shares Sunday market leadership with the Sun on Sunday, will say: "For a safer, freer, more prosperous - and yes, an even Greater Britain: why we urge you to vote Remain", David Rose said in a message on Twitter.

The broadsheet Sunday Telegraph, which occupies a similar right-of-center position but sells 371,000 copies against 1.4 million for the Mail on Sunday, came out for "Leave" on Saturday.

(Reporting by Paul Sandle; editing by William Schomberg)