The US army admitted today that it had removed data about air strikes in Afghanistan from its monthly air power summaries.
US Central Command, which oversees the Afghanistan war, claimed that the data had been removed because it was "disproportionately focused" on the use of weapons by drones.
It said the decision to stop reporting drone strikes was taken with the International Security Assistance Force - the Nato-led coalition in Afghanistan.
President Barack Obama's government has increasingly used drones but civilian deaths from strikes have raised ethical concerns and angered local populations.
Some politicians have also questioned the legality of targeted killings and whether drones would allow the killing of US citizens, even inside the US itself.
The debate was intensified by President Obama's decision to nominate chief counter-terrorism adviser John Brennan, an architect of the drone campaign, as new CIA director.
Foreign Minister Alistair Burt's admission that the Cameron government has "supported" a survey of attitudes to US drone strikes in Pakistan's tribal areas amounts to a tacit admission of British involvement.