The UK's telecom regulator, Ofcom has pushed back the country's radio spectrum auction by at least three months following rumoured threats of legal action from the main mobile networks.The auction paperwork was due to be published by the end of this year, but will now be published sometime in the first quarter of next year, with the auction itself taking place about thee months later.

The auction - offering 800MHz and 2.6GHz spectrum blocks -- is estimated to raise upwards of UK£3 billion for the government.

An Ofcom spokesman told The Guardian newspaper: "The spokesman added: "This is a complex area, involving a large number of technical and competition issues that we need to consider and resolve before finalising proposals. For example, a very high proportion of households in the UK rely on Digital Terrestrial TV -- Freeview -- which needs to be relocated before 4G can be rolled out."

O2 has warned that it considers the way the auction is being structured -- which will impose a spectrum cap on spectrum below 1Ghz -- could be seen as illegal state aid for Hutchison 3G UK, who would be able to pick up more of the 800Mhz spectrum than its rivals.

"We note that because these technical issues need to be satisfactorily resolved before new networks can be built, it will not be possible for mobile operators to start rolling out 4G networks until 2013 at the earliest regardless of when the auction itself actually takes place."

Yesterday, the country's smallest mobile network, Hutchison 3G UK (Three) warned that a delay would be particularly detrimental to the company as it lacks the lower frequency spectrum that its rivals have, and were recently permitted to run 3G services over.