As elections in the coming months accelerate efforts to build democracy in Iraq, violations of international law there and the failure of the British and American governments to discourage them are a grave setback.

I refer to the plight of 3,500 members of an Iranian opposition group, the PMOI, based at Camp Ashraf, 60km north-east of Baghdad, who in 2004 were recognised as "protected persons" under the Fourth Geneva Convention. Since then they have been entitled to expect that their safety and security would be guaranteed by US and other coalition authorities, who remain clearly bound by that responsibility.

On 28 and 29 July, these innocent civilians, of whom 1,000 are women, and many are children, were subjected to a violent attack on their camp by Iraqi forces, who used bulldozers to gain entry to the camp and then savagely assaulted the unarmed inhabitants with axes, chains, and wooden planks while firing live ammunition. Eleven of the residents were killed, more than 500 injured and 36 abducted and imprisoned without any form of legal process. The attack was filmed on mobile phones, so the scale of the attack and the identity of some of its perpetrators are beyond dispute.

The residents looked in vain to the British and US authorities to defend them. Whitehall and the White House have remained silent in response to widespread demands for their intervention.

The US and British governments have attempted to shift responsibility to the Iraqis, claiming that their duty ended with the transfer of legal authority, but neither the Fourth Geneva Convention nor the basic principles of international humanitarian law entitle them to do this.

The convention duty imposed upon an occupying power in time of war to guarantee the safety of protected persons is absolute. Until recently the US and other coalition governments recognised this and acted upon it. Yet in January 2009 they purported to hand over their responsibility to the Iraqis. They relied on receipt of firm guarantees that the residents of Camp Ashraf would continue to remain unharmed.

Despite warnings by British parliamentarians such as Lord Corbett, who have kept closely in touch with the situation in Camp Ashraf, that the complete withdrawal of the US and Britain would place the residents in mortal danger, the handover to the Iraqis was allowed to proceed. Even if the occupying powers accepted Iraqi assurances in good faith, they were cynically and culpably deceived, as the tragic outcome makes only too evident.

Article 45 of the convention places a continuing responsibility on the transferring state. It was specifically designed to enable a transferring state to require the transferee state to carry out its obligations. The non-refoulement principle of international law is to the same effect. A state may not even send an individual back to his or her own country where to do so would be to place that individual at risk of illegal treatment. The threat to the residents of Camp Ashraf of return to Iran is a very real one. That may well be the intention of the Iraqis in collusion with the Teheran regime. The fate of the residents will be laid at the door of the US and British governments if their present inaction allows the threat of forcible repatriation to Iran to be carried out.

This is a desperate human crisis. There is no time to lose. The US and British governments must now urgently implement Article 45 of the Fourth Geneva Convention to protect the Camp Ashraf residents from further violence and from eviction. They must enlist the assistance of the United Nations and in particular the United Nations Assistance Mission for Iraq (Unami) to establish a full-time protective presence within the camp.