The discovery of government papers from the early years of the Northern Ireland Troubles has sparked a court action by former prisoners held without trial under the controversial policy of internment.

Six former internees who have reported being tortured by British troops are suing the Ministry of Defence, the Secretary of State, the police, as well as the estate of the late Brian Faulkner, former Northern Ireland prime minister.

The group, who see their action as a test case for the 2,000 people interned in the early 1970s during some of the worst years of violence, said the confidential documents confirmed their long-standing belief that the policy was directed against the Catholic community and included indiscriminate arrests.

One man recounted having barbed wire wrapped around his wrists before he was hooded and beaten by troops, while a woman jailed without trial recalled the trauma of having to sign her two children into care.

Solicitor Padraig O Muirigh said his clients were launching proceedings on the 40th anniversary of internment, which began on August 9 1971. And while it was ordered by Mr Faulkner, the policy was continued by Westminster politicians for four years after they stepped in to take over the running of Northern Ireland.

Mr O Muirigh said: "These papers demonstrate not only the existence of a discriminatory policy against the nationalist community, but also the indiscriminate nature of the arrests by the Army, who were clearly instructed to arrest without question those in a household over the age of 18 in circumstances where there was uncertainty over the identity of the person being sought out by the Army."

Internment was introduced as the authorities struggled to cope with spiralling levels of violence and was billed as a bid to take paramilitaries off the streets. But weak intelligence meant many of the key targets escaped and people without any involvement in violence were arrested.

A total of 1,981 people were detained over the period, with 1,874 internees drawn from the Catholic community, while 107 were Protestant.

A document from 1974 recording a meeting of the Northern Ireland Office, but which included the Attorney General, the Home Office and the Ministry of Defence, showed officials asking "why only Roman Catholics were interned before 1973".

The reason given was that "in the view of the security forces there was no serious Protestant threat in that period of a kind which led to death and serious injury". This was despite the fact that by the end of 1972 loyalist paramilitaries had killed 150 people.