The UK government will force through plans to introduce national roaming into law this week, letting customers in rural areas switch to a rival network when in so-called rural 'notspots'.

Culture secretary Sajid Javid will announce the plans later this week after mobile phone operators failed to come up with an alternative suggestion. The Sunday Times reports that the four big operators - EE, O2, Three and Vodafone will be required to share mobile phone masts in rural areas where coverage is poor.

Customers will be able to connect to the network with the strongest signal, regardless of which network that is. The law will be published as part of a public consultation document although it isn't clear when customers will benefit from the plans.

An unnamed source told the paper: "We're keen on a national roaming plan. We’ve talked to the mobile phone networks and told them to come up with a plan. The secretary of state is pretty frustrated that they have failed to do so.

"We’ve given them numerous opportunities to find a solution. The lack of movement from the mobile phone operators means we now need a legislative option to deal with the issue of partial notspots.”

Plans for national roaming were first floated back in June, with mobile phone networks dismissing them out of hand. Concerns have been raised that sharing mobile infrastructure between networks will remove the incentive to build more masts to improve coverage.

It is hoped that the proposals will benefit about 1m customers in around 20 per cent of the country where mobile signal isn’t up to scratch. Networks have previously said that implementing new technology for national roaming would be complicated and expensive and that it is likely to lead to higher bills and disruption.