LONDON — Carlton Communications Plc. and Granada Group Plc. are set to oppose government rules requiring them to cut their holdings in Britain’s commercial TV news network ITN by the end 1994, media sources said Wednesday.“We want to maintain our stake,” said a source at Carlton, which led a consortium in a $ 45 million takeover of ITN last March. Carlton and Granada each have a 36% stake of Independent Television News (ITN). ITN was owned by the independent television broadcasters. Since the takeover, Carlton and Granada have doubled their stakes via their own takeovers of Central Independent Television and LWT (Holdings) Plc., respectively. Carlton and Granada are now the biggest shareholders with 36% each. Reuters Holdings Plc. has 18% and MAI Plc., which has taken over Anglia Television Group , and Scottish Television Plc., have 5% each. Current legislation says a company other than a commercial broadcaster should hold a majority stake in ITN by the end of 1994 and no shareholder should have more than 20%. Heritage Secretary Peter Brooke is carrying out a review of cross-media ownership rules. The commercial TV regulator, the Independent Television Commission, has recommended that the restriction to 20% of individual holdings in ITN be retained, but the rule requiring ITV license holders to hold less than 50% collectively should be scrapped.