LONDON—Britain accused Russian news channel RT on Wednesday of being a tool of a Kremlin disinformation campaign and asked the UK media regulator to take action if needed after Russia recognized two rebel regions of eastern Ukraine. Russian officials say RT is a way for Moscow to compete with the dominance of global media companies based in the United States and Britain that Moscow says offer a partial view of the world. Critics say RT, which broadcasts news in English, Arabic, Spanish, and German, is the propaganda arm of the Russian state and aims to undermine confidence in Western institutions. Culture Secretary Nadine Dorries said in a letter to state media regulator Ofcom that she was concerned RT would seek to spread “harmful disinformation” about the Russia–Ukraine crisis. “While respecting Ofcom’s regulatory independence, I call on you to ensure your actions are timely and transparent to reassure the British public,” …