New research shows that the increase in mobile phones in the developing world has sidelined tens of millions of people.

The study was undertaken by scientists from Strathclyde and Manchester universities and found that despite the benefits of mobile phones, the "haves" in Africa's informal sector are getting richer, while the "have-nots" are losing income.

Professor Richard Heeks, director of Manchester University's Centre for Development, said in a statement: "The benefits of mobile phones to the developing world are huge as they are used as a primary form of communication: landlines are much less common.

"But that growth does not reach everyone and without a mobile, you are cut off socially and economically.

"We talked a few years back about the 'digital divide', now we are recognising the mobile divide."

Dr Abi Jagun from Strathclyde University's Department of Management Science examined the experience of a group of workers in Nigeria's informal cloth-weaving sector.

This industry centres on the weaving of ceremonial dress for special occasions such as births and marriages and employs tens of thousands of people.

Dr Jaguan said: "The mobile divide was brought out starkly in our interviews with the weavers. The places where the cloth is produced are often located some distance from where they are consumed, and intermediaries are used to sell the end product.

"We found that weavers who owned a mobile were able to stay in constant touch with their business contacts, which dramatically cut the number of journeys to meet thread suppliers, traders and customers.

"But weavers without a mobile were forced to go on costly and sometimes dangerous journeys, making it increasingly hard to obtain orders."

Many weavers who made these long journeys arrived at their destinations only to find that available orders had been assigned by phone to someone else. Weavers who do not have a phone or access to a phone are losing business and income.

Dr Jaguan added: "The value of mobile phones in Nigeria can't be quantified in monetary terms alone. Along with the contribution they can make to securing livelihoods they are also important in reducing the vulnerabilities that people face as a result of lack of information and isolation."