LONDON, April 29 (Reuters) - Lawyers for former detainees are preparing to sue the British government and intelligence services for alleged complicity in abuse of terrorism suspects by the United States and Pakistan.

The cases, if they reach court, would be among the first anywhere to examine alleged wrongdoing by spy agencies in the U.S.-led “war on terrorism”. Similar lawsuits in the United States have been thrown out on grounds of national security.

Lawyers for eight former inmates of the U.S. Guantanamo Bay prison camp in Cuba are launching proceedings to sue Britain for alleged complicity with their abduction, ill-treatment and interrogation, sources familiar with the case say.

Five are British and three are foreign nationals living in Britain.

And Salahuddin Amin, a British man who is appealing against his conviction last year for involvement in an al Qaeda-inspired bomb plot, is preparing a civil action alleging British acquiescence in what he says was torture by Pakistan’s ISI security agency, his lawyer Tayab Ali said on Tuesday.

“The civil action will take the form of suing members of the British government, establishment, who we feel are responsible for his treatment, or who acquiesced to it at the very least -- failed in their duty to prevent that from happening,” Ali said.

“We have a list of individuals, some of whom are named, that we intend to process against,” he added in a telephone interview.

In an account of his treatment, published in The Guardian newspaper, Amin said he was held for 10 months by Pakistan’s ISI in 2004 and subjected to repeated torture sessions, including savage beatings and being threatened with an electric drill.

These were interspersed with interviews with two members of Britain’s MI5 intelligence service, calling themselves Matt and Chris, at which Amin said he would be asked the same questions, and give the same replies, as in the preceding torture sessions.

Britain and the United States deny allegations by human rights groups that they have “outsourced torture” by exploiting intelligence information extracted from terrorist suspects held in countries where prisoner abuse is rife.

British intelligence officers have questioned suspects held by third countries, but “we never use torture under any circumstances and we never instigate others to commit it”, a security source said.

“We don’t comment on individual cases but we do take our responsibilities very seriously. All our staff ... are fully committed to complying with the requirements of the law when working at home and overseas.”

Amin raised the torture allegations at his London trial, which ended in April last year, but was convicted with four others. British security agents responded to his charges but their evidence was given in camera, with the press excluded.

The Guardian said two other Britons formerly held in Pakistan on suspicion of terrorism have alleged they were tortured there. One said he had three fingernails pulled out with a pair of pliers. (edited by Richard Meares)