GlaxoSmithKline, the UK’s largest drugs company, has been asked to pool its patents for HIV medication.

Fiften organisations, including Christian Aid, Unicef, Stop Aids Campaign and Médecins Sans Frontières (Doctors Without Borders), have signed a letter to the company which says millions of lives in developing countries could be saved by the move.

The patent pool is being put together by Unitaid and would allow cheap copies and combinations of AIDS medication to be produced with no legal restrictions. Currently, drugs companies can hold a monopoly on their medicines for 20 years, after which time patents run out.

In an interview with the Guardian last week, GSK chief executive Andrew Witty said he did not know much about Unitaid, the organisation working to improve drugs in developing countries. He added that no one had yet put a “concrete proposition” about patent pools in front of him.

However, he expressed some reservations about the idea, saying GSK was already working to fight AIDS, especially around medication for children, and has slashed the company’s drug prices to no more than a quarter of western prices.

Witty said he had already opened a patent pool for “neglected” diseases which anyone can access, but this does not contain the firm’s patents for HIV medication.

In reply, the letter from aid groups said: “GSK’s insistence that a patent pool for HIV is unnecessary is surprising given the woeful lack of innovation into HIV treatments suitable for children and the obvious need for new safer and more effective fixed dose combinations for adults.” The letter also asked him to meet Unitaid.