LONDON (AP) In a new claim of British complicity in rights violations overseas, a human rights group took legal action Monday against the British government, accusing it of passing on intelligence to help deadly U.S. covert drone attacks in Pakistan.

The challenge is the latest in a string of lawsuits against U.K. spy agencies for sharing intelligence with foreign governments including the late Moammar Gadhafi's regime in Libya in ways that may have put victims in lethal danger.

The London-based charity Reprieve and the law firm Leigh Day & Co. filed papers to the High Court claiming that civilian staff at Britain's electronic listening agency, GCHQ, could be "secondary parties to murder" for providing "locational intelligence" to the CIA in directing its drone attack program.

Reprieve was acting on behalf of Noor Khan, 27, a Pakistani whose father was killed by a drone strike in northwest Pakistan in March 2011 while attending a gathering of elders. More than 40 other people were killed in that attack, the group said.

The nonprofit group, which helps death row prisoners and Guantanamo Bay inmates, urged the British government to be more transparent about its role if any in the drone program.

"What has the government got to hide? If they're not supplying information as part of the CIA's illegal drone war, why not tell us?" director Clive Stafford Smith said.

British officials have never commented publicly on the drones. The Foreign Office and GCHQ declined comment on the legal action Monday, saying they could not speak about ongoing legal proceedings or intelligence matters.

Since 2004, CIA drones have targeted suspected militants with missile strikes in the Pakistani tribal regions, killing hundreds of people. The program is controversial because of questions about its legality, the number of civilians it has killed and its impact on Pakistan's sovereignty.

U.S. officials do not publicly acknowledge the covert drone program but they have said privately the strikes harm very few innocents and are key to weakening al-Qaida and other militant groups.

Leigh Day & Co. did not detail what evidence it has regarding Britain's alleged role in the drone program, but cited media reports that quoted an anonymous GCHQ source as saying that the assistance it gave to the U.S. authorities was in 'strict accordance' with the law.

The law firm disputed that, saying GCHQ staff may be guilty of war crimes by passing along detailed intelligence to a drone program that potentially violates international humanitarian law.

Experts say, however, there are multiple problems in trying to determine Britain's liability in such cases. There is not yet an established view of the legality of the drones, and it would be difficult to determine whether the agents who passed on the information knew that their actions would lead to airstrikes or torture, rendition and other rights violations in other cases.

"In theory it is possible that they (British agents) are responsible, but in practice these issues are very difficult to resolve," said Antonios Tzanakopoulos, a law lecturer at University College London. "You would need to show that when passing information, the U.K. knew or ought to have known that its action would have certain consequences."

Last year, British spy agencies were accused of sharing sensitive information with Gadhafi's regime, leading to the torture or rendition of two Libyan men and their families. Before that, former Guantanamo detainee Binyam Mohamed accused the British government of complicity in his alleged torture by U.S. agents.

Investigators in the U.K. concluded there was evidence that British agents provided information to the U.S. authorities about Mohamed and also supplied questions for them, but that there was not enough evidence to charge anyone in a criminal court.