Orange and T-Mobile owner Everything Everywhere, which has been renamed as EE, will make the state-of-the-art technology available to some 20 million people in 16 cities across the UK.
Unveiled at the Science Museum in London, the 4G network, which offers speeds up to five times faster than 3G, will be available on HTC, Samsung, Nokia and Huawei devices, as well as "one more to come", which is widely expected to be Apple's iPhone 5.
The announcement is likely to enrage EE's competitors, including Vodafone, 3 and O2, who have threatened legal action over telecoms regulator Ofcom's decision last month to allow EE to launch 4G on its existing network.
The 4G services will allow uninterrupted access to the web on the go, high definition movies to be downloaded in minutes and TV to be streamed without buffering.
Four cities - London, Bristol, Cardiff and Birmingham - are switched on on Tuesday for the company's engineers to begin live testing and systems integration in readiness for the customer launch.
EE gave no specific date but said 4G will be available to its customers by Christmas in London, Edinburgh, Cardiff, Belfast, Birmingham, Bristol, Derby, Glasgow, Hull, Leeds, Liverpool, Manchester, Newcastle, Nottingham, Sheffield and Southampton.
The group plans to roll out the service to further towns, cities and rural areas next year, with population coverage of 70 per cent and rising to 98 per cent in 2014.
Source: MEN Business