LONDON (Reuters) -Britain’s media regulator on Monday launched 15 investigations into the output of Russian-backed television channel RT over the impartiality of its coverage of the invasion of Ukraine. Ofcom expects any media organisation with a licence to broadcast in Britain to provide a significant range of voices to maintain impartiality. The European Union on Sunday proposed banning RT and news agency Sputnik to prevent what it said was Russian propaganda. But Britain has warned that that approach could lead to a reciprocal ban by Moscow against the BBC and others. “Given the serious on-…