Evidence was growing this weekend that babies born in the Iraqi city of Fallujah – scene in 2004 of one of the few set-piece battles of the invasion – are exhibiting high rates of mortality and birth defects.

In September this year, say campaigners, 170 children were born at Fallujah General Hospital, 24 per cent of whom died within seven days. Three-quarters of these exhibited deformities, including "children born with two heads, no heads, a single eye in their foreheads, or missing limbs". The comparable data for August 2002 – before the invasion – records 530 births, of whom six died and only one of whom was deformed.

The data – contained in a letter sent by a group of British and Iraqi doctors and campaigners to the United Nations last month – presaged claims made in a report in The Guardian yesterday that there has been a sharp rise in birth defects in the city. The paper quoted Fallujah General's director and senior specialist, Dr Ayman Qais, as saying: "We are seeing a very significant increase in central nervous system anomalies... There is also a very marked increase in the number of cases of brain tumours." Earlier this year Sky News reported a Fallujah grave-digger saying that, of the four or five new-born babies he buries every day, most have deformities.

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The campaigners' letter to the UN calls for an independent investigation to be set up, "the cleaning up of toxic materials used by the occupying forces, including depleted uranium and white phosphorus", and an inquiry launched to discover if any war crimes have been committed.

The campaigners believe that either white phosphorus or depleted uranium is a major, if not only, cause of the birth defects. White phosphorus, which US military has admitted firing on insurgents in heavily populated Fallujah, has a long history of military use, dating back to the First World War.

And although no scientific study has ever proved a causal link between depleted uranium and serious medical problems – and several studies seem to have proved the opposite – it is by no means in the clear. Ever since the first Gulf War, its use has been linked to cancers among returning troops.