Next generation mobile phones will disrupt digital television when they launch in 2013 unless the companies do something about it, the communications watchdog warned yesterday. Ofcom yesterday set out proposals to reduce interference between digital TV and 4G mobiles, saying it wanted to ensure the two services could function alongside each other. It warned that if nothing was done, 760,000 homes across the UK could be hit by interference to the TV picture quality of their Freeview service. Some viewers will have to fit a filter to their television aerial to block the interfering signals, while mobile base stations may also have to be changed. The mobile operators will be called upon to bear the costs, the regulator said. It added that in a very small number of cases the filter may not work, and the customers will have to switch to a satellite service, such as Freesat. Ofcom has launched a consultation, which closes in August, and it expects to publish an update some time during the autumn. The 800 MHz spectrum freed up by the digital TV switchover next year will be offered to mobile operators in an auction run by the regulator next year. The frequency is vital for companies looking to offer a 4G, or Long Term Evolution, mobile service. 4G will dramatically improve browsing the internet on the move. The regulator said it was \"essential\" to meet the rapid growth in data traffic as use of mobile broadband and smartphones increases. Yet the first handsets offering 4G services are unlikely to appear before 2013. Yet, fears have been raised that the 800 MHz frequency is close to those used for digital terrestrial television broadcasting, and the signal could interfere with set-top boxes and digital televisions. Ofcom estimated that up to 3 per cent of digital terrestrial viewers could see their service deteriorate if nothing is done to solve the problem. The regulator has been aware that 4G phones could cause problems to digital TV for some time, and commissioned Cobham Technical Services to carry out extensive tests last year on their effect on cable television. It previously said it was \"keeping a close eye on the situation\".