Environmentalists have threatened to sue Apple if it does not make its iPhone a "greener" product or tell consumers of the toxins allegedly used in the device's manufacture.

The Centre for Environmental Health (CEH), a campaign group based in Oakland, California, said that it would begin a lawsuit in 60 days unless Apple took action.

The threat comes after a report by Greenpeace, the environmental organisation, which alleged that the iPhone contained dangerous levels of bromine, chlorine and phthalates - chemicals used to increase the flexibility of plastic.

David Santillo, a senior scientist at Greenpeace, said in a video posted on the campaign group's website: "Electronics companies have traditionally relied on the cool, clean image of their devices in order to sell them. What we have found over the years is that once you get behind that shiny cover, the story is very different."

The level of phthalate esters, which are linked to birth defects, in the plastic coating of iPhone headphone wires is greater than that allowed in toys or childcare items sold in Europe, Greenpeace alleged.

The CEH's website said that it "works to hold corporations accountable for their use of toxic chemicals that endanger public health".

It added: "We challenge corporations to stop polluting or to lower the toxicity of their consumer products. We motivate change by outreach, education, and when necessary, legal action under California's Safe Drinking Water and Toxic Enforcement Act [otherwise known as ‘Proposition 65']."

A notice sent to Apple and the California Attorney-General gives the group legal standing to sue Apple in 60 days. A lawsuit could force Apple to put warnings on iPhone packaging, but is unlikely to lead to a product recall.

An Apple spokesman said: "Like all Apple products worldwide, iPhone complies with RoHS [the EU's Restriction of Hazardous Substances directive], the world's toughest restrictions on toxic substances in electronics." The spokesman added that Apple had already pledged to eliminate the use of PVC and brominated flame retardants by the end of next year.

The campaigners' action may prove embarrassing for Al Gore, a member of Apple's board, who last week won the Nobel Peace Prize for his work on climate change.

Apple has sold more than a million iPhones since the device's launch this summer in the US. This month an iPhone buyer that said she was suing Apple for $1 million (£490,000) after the company cut the price of the device by $200 only 68 days after its American launch.

Only hours after Steve Jobs, Apple's chief executive, unveiled the gadget in January, Apple was sued by Cisco, which claimed that it owned the "iPhone" brand. The technology companies settled out of court.

Green calls

2003 Greenpeace first contacts Apple on chemicals policy

2004 Apple graded red (worst) by Greenpeace on chemicals use

2007 More than 70 non-governmental organisations ask Al Gore, a member of Apple's board of directors, to support environmental resolutions filed for the company's annual meeting. They are unanimously rejected