They are solar-powered, made from recycled plastic water bottles and capable of measuring your carbon footprint - and when the annual Mobile World Congress began in Barcelona yesterday, environmentally friendly mobile phones led the agenda.

With demand for the latest handsets set to slump by 10 per cent this year, mobile phone makers attending the conference were looking for new ways to drive their profits through the recession.

Samsung unveiled its Blue Earth phone, the first solar-powered model in history. Designed to look like a “flat and shiny pebble”, it allows users to flaunt their environmental credentials as effectively as a Greenpeace T-shirt. The “eco walk” function, for instance, can count how many steps you have taken and the amount of carbon dioxide you have saved by not travelling by car.

Samsung claims that the phone's solar panel can deliver enough power to enable users to make a call anytime, anywhere. Blue Earth, which will be available this year for a price that has yet to be disclosed, is made from recycled plastic water bottles.

Other manufacturers are displaying green products. ZTE, a Chinese vendor, will announce today a collaboration with Digicel, the mobile operator, and Intivation, a Dutch start-up company, to offer a solar-powered handset specifically to developing countries.

The phone, which will be priced at about £15, is being marketed to consumers who lack reliable access to electricity. Donald Fitzmaurice, the chairman of Intivation, which developed the solar panels, said: “There are 1.6billion people in the world who can't get electricity. You empower them by giving them a phone as well as letting the operators increase their market.” The phone will go on sale in June in the Caribbean and in the South Pacific.

Campaigners have voiced concerns for years about the environmental impact of mobile phones. More than three billion people use mobile phones and, with many replacing them every year, there is a huge amount of waste.

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