A senior Gover nment minister has attacked US president Barack Obama's policy of drone strikes against al Qaida and Taliban leaders in Pakistan.
Liberal Democrat Cabinet minister Ed Davey claimed the US was "transgressing the sovereignty" of Pakistan by launching weapons from drones at targets in the country.
The Energy Secretary said the use of drones by the US military was setting a "very dangerous precedent" and claimed international law needed to catch up with the technological advances in unmanned aerial vehicles.
Appearing on BBC1's Question Time Mr Davey said: "On drones I think there's a serious question we have got to face up to. Because I think if the Americans keep using drones in the way that they have been doing everyone is going to say this is setting a very, very dangerous precedent.
"I think the UN and the international community has got to look very seriously at these weapons. They are transgressing sovereignty, in the case that we know about America, the sovereignty of Pakistan.
"And while drones can be, if they are not being used in a military way ... used for surveillance in a very effective way, and that's how the British use them, I think there are some real serious issues, (about) the international law of the use of drones and the American government is beginning to look at that."
Britain uses drones to carry out military strikes, with official figures showing that the UK's unmanned aircraft flew 892 missions last year in Afghanistan, with weapons being fired on 92 occasions - more than 10% of all sorties. But ministers have insisted that British drones are not used to carry out operations in Pakistan.
Mr Davey said: "There are strict rules of international engagement and conflict. My concern with drones is that the international law has not caught up with them and it must do, so that people who are using these types of technology actually have to abide by the law."
He added: "Americans in their armed forces are saying 'we have got to make sure that we don't set a precedent so other countries start doing what we're doing with drones because that would be very dangerous'."
Last month t wo United Nations human rights investigators called for more transparency from the United States and other countries about their drone strikes programme.
Ben Emmerson and Christof Heyns, who presented two reports on the subject at the UN, also called on other countries to speak up about when deadly drone strikes are acceptable.
They said the lack of consensus risked creating anarchy as more countries acquired the technology.
Mr Emmerson, the UN special rapporteur on human rights and counter-terrorism, said the US justified some drone strikes against terrorist targets in other countries by arguing that it was engaged in an armed conflict with al Qaida with no boundaries.
He said other countries disagreed with that analysis but few had spelled out their own positions.
''We all recognise that the moment other states start to use this technology in similar ways, we are facing a situation which could escalate into a breakdown of peace and security,'' he said.
In his report, Mr Emmerson said he received statistics from the Pakistani government indicating that at least 2,200 people had been killed in drone strikes in that country since 2004, at least 400 of whom were civilians.