William Hague questioned on Pakistan drone strikes
The Government is coming under increasing pressure to reveal if the UK is providing intelligence to help the US carry out drone strikes in Pakistan.
Lawyers for the son of a man killed in such an attack have written to the foreign secretary William Hague wanting to know what the UK's policy is.
Pakistan has called the strikes, which the US does not publicly acknowledge, a violation of its sovereignty.
The Foreign Office says it will study the letter closely before responding.
The law firm Leigh Day & Co is acting on behalf of Noor Khan, whose father was killed earlier this year in a drone strike on a jirga - or council of elders - in north-west Pakistan.
Richard Stein, head of human rights at the firm, said he wanted to know whether any information was being passed by agents of the UK Government to US Government forces to assist in the attacks.
He said: "This legal action simply looks to ask a number of questions of our government regarding UK involvement in the drone strikes in Pakistan."
American officials have privately said that the CIA's drone programme has killed many Taliban and al Qaeda commanders.
Mr Stein said it was estimated the attacks had killed thousands of people "within a country we are not militarily engaged with", he said as a result they were against international law.
"Unless it is categorically denied that the UK continues to pass such information to the US Government forces, we require a clear policy statement of the arrangements which are in place and circumstances in which the UK considers it to be lawful to do so," he said.
International human rights campaigners have also condemned reports of innocent civilian casualties in drone strikes.
The director of the legal action charity Reprieve, Clive Stafford Smith is backing the call for more information.
He said: "CIA drone strikes are killing hundreds - if not thousands - of civilians and destabilising Pakistan.
"The British people have a right to know what their country's policy is regarding our involvement in this illegal and disastrous campaign."
An FCO spokesperson said: "We will study this letter closely and respond to the issues raised."