Apple has refused to allow its iPhones to be included in the UK's first-ever green ranking scheme for mobile phones.

The scheme gives phones a rating of zero to five based on their environmental footprint and major manufacturers including Nokia, Sony Ericsson and Samsung have signed up. The network O2, which is launching the rating system today, said 93% of the devices its customers use will be covered.

Launched in partnership with sustainability advisers Forum for the Future, the green ranking scheme scores handsets on the ecological impact of their raw materials, the manufacturing process, packaging, how long they are likely to last, energy efficiency and how easy they are to reuse or recycle.

An Apple spokeswoman declined to comment on why the company had decided not to join the voluntary labelling scheme, but highlighted its environmental reporting online.

Many other mobile phone manufacturers, including market leader Nokia, publish similar environment reports online and are taking part in the rankings. RIM, the Canadian firm that produces the Blackberry, has pledged to joint the scheme next year.

"Transparency is always an issue for consumer electronics companies, who claim that providing too much information gives away competitive advantage. But consumers also deserve to know the full story. While Apple has recently made important strides in eliminating toxic chemicals from its products and the reporting of their environmental footprint, it still lags behind others in transparency," said Gary Cook, IT sector analyst for Greenpeace International.

The environmental group loudly lobbied the California-based company with its "Green my Apple" campaign, and in 2007 praised Apple CEO Steve Jobs for his decision to phase out the use of brominated flame retardants and PVC in the manufacture of the company's products.

The ratings in the scheme are based on answers by manufacturers to a questionnaire of 63 questions, in a bid to "turn complexity into something simple to understand", said James Taplin, principal sustainability adviser at Forum for the Future. The energy and resources used to produce the phone, for example, are partly measured by the "proxy measure" of the area of integrated circuits in each phone. "The largest impact comes from the energy used in extracting materials [from the Earth] and transporting them, as well as the energy and water used to process components such as silicon wafers," said Taplin.

Using the methodology, O2 rated the Sony Ericsson Elm the most sustainable mobile phone with 4.3 out of five. The phone's pole position was achieved by its high score on one criterion – "functionality" – which sees it negate the need for separate devices such as a camera, MP3 player and satnav, saving the energy that would be required to make them. "You need to look at the indirect impact of the phone, such as fewer devices, not just the phone," added Taplin.

Seven phones tied in second place with a score of 4.0: the Nokia 1800, Nokia 6700, Nokia C7, Samsung GT-S8500, Sony Ericsson Xperia X10 mini, Sony Ericsson Xperia X10 mini pro and Sony Ericsson Zylo. Apple estimates the production and use of each iPhone 4 produces 45kg CO2e over its lifetime.

The mobile phone industry as a whole is belatedly attempting to green its image, with the big five UK networks and handset makers pledging last year to phase in a universal charger that must also meet energy efficiency standards.

There are signs that consumers want greener phones – 11.5% of people surveyed for O2 said sustainability had a "strong influence" on which model they would buy. Ronan Dunne, O2's UK chief executive, said: "We know that sustainability is important for many of our customers and for the first time [with the eco rating scheme] they will have the whole picture from which to make a full and balanced purchasing decision."