By Paul Sandle and Ankush Sharma
(Reuters) - The British government said on Wednesday it could force mobile phone network operators to improve coverage in rural parts of the country for simple voice calls and text, eliminating so-called "not-spots".
One possible solution would be to introduce a compulsory national roaming plan which would switch users' phones to whichever network gives the strongest signal, the government said, in announcing a range of proposals.
The government has set a deadline of Nov. 26 for the industry and other interested parties to respond.
"It can’t be right that in a fifth of the UK people cannot use their phones to make a call," said Sajid Javid, the Secretary of State for Culture, Media and Sport.
"The government isn’t prepared to let that situation continue," he said.
Network operators, however, who have spent billions of pounds on building their networks, are fiercely opposed to sharing them with rivals.
EE, the country's largest mobile operator, said national roaming would affect network reliability and might also lead to price rises. EE is a joint venture of Deutsche Telekom and France's Orange SA.
Vodafone agreed, saying such a scheme would be technically far more complex than international roaming, slow to implement and could cause problems with network resilience.
"National roaming would also be extremely challenging from a legal and regulatory perspective as UK mobile operators have paid the government hundreds of millions of pounds for spectrum licences on the basis of existing regulation founded on the principle of competing networks," the company said.
The three other options proposed by the government are: to increase infrastructure sharing by enabling operators to put transmitters on each other's masts; obliging the networks to cover a certain percentage of the UK; giving mobile virtual network operators (MVNOs) access to all four of the national networks.
Analyst Matthew Howett at consultancy firm Ovum said a combination of infrastructure sharing and tougher obligations was the most likely outcome of the consultation.
"While national roaming sounded attractive to those with coverage issues, it is a messy solution that ought to be abandoned," he said.
He also noted that the government's plan only dealt with voice services carried on older 2G networks.
Licences for new 4G mobile broadband services include tougher obligations, for example a requirement in one licence to serve 98 percent of the population by 2017.
The lower frequencies used for 4G services also range over larger areas, making them better for rural coverage, although 4G networks do not yet carry voice calls.
As well as upsetting the mobile industry, Javid's proposals also put him on a collision course with a ministerial colleague, according to a report in The Times on Wednesday.
The paper said that a confidential letter it has seen from Home Secretary Theresa May said the proposals by Javid for switching networks could jeopardise the fight against terrorism, by complicating the ability of security agencies to intercept suspect calls.
National roaming, and another proposal to allow a company to launch services using all four networks, "could have a detrimental impact on law enforcement, security and intelligence agency access to communications data and lawful intercept", the newspaper quoted her as saying.
The Home Office said it would not comment on a leaked document.
(Additional reporting by Kylie MacLellan; Editing by James Dalgleish and Greg Mahlich)