An environmental group is planning to sue Apple over hazardous materials used in the iPhone unless the company changes the design.

The Center for Environmental Health (CEH) has warned Apple to stop using brominated flame retardants (BFRs) and PVCs in the iPhone within 60 days or face legal action.

The group is not seeking a product recall, but wants warning stickers put on all iPhones to alert users to the alleged risks.

BFRs are used internally in the iPhone to deal with heating issues but their use has been discontinued by most mobile phone manufacturers.

PVCs, which Apple uses in the iPhone headphones, have been shown to cause birth defects in animals and are banned in children's toys in Europe.

"If a pregnant woman is winding and unwinding that cord a number of times each day, like we all would, she is getting exposed to this chemical," said CEH chief executive Michael Green. "That is a big piece of our concern."

Apple has already promised to phase out the use of such materials by the end of the next year, but the CEH wants much swifter action.

The iPhone controversy started after Greenpeace issued a report detailing the environmental cost of the iPhone. Other criticisms include the practice of soldering or gluing the battery into the iPhone, making recycling much more difficult.

Greenpeace has condemned Apple for having one of the worst environmental records in the technology industry.

The environmental group put Apple bottom of the table in April for environmental awareness in technology, although that rating has been raised recently.