A senior Government official believed John Hume wanted internment brought back to tackle IRA violence, official papers reveal.
Just two months before he became SDLP leader in 1979 and 10 days after Lord Mountbatten's killing and the notorious Narrow Water massacre, the Derry politician reportedly suggested a return to detention without trial.
Foreign Affairs documents released from the National Archives show Irish diplomat David Neligan believed Mr Hume supported the controversial tactic to lock up suspected terrorists.
In a briefing note on the meeting, the civil servant warned colleagues that Mr Hume's controversial stance had not been thought through.
"Hume expressed particular revulsion for the IRA whose recent atrocities were directly responsible for the extreme attitudes now being revealed by public opinion in Britain and amongst unionists," Mr Neligan wrote.
"His (Mr Hume's) thoughts were evidently running towards the idea of internment as a solution to the IRA violence.
"The authorities could publish names of suspected members of illegal organisations and require them to announce publicly that they had severed all connections with those bodies or, alternatively, be interned.
"In this and other respects Mr Hume's ideas to cope with the immediate grave situation did not seem to have been fully thought through."
Mr Hume succeeded Gerry Fitt as party chief in November 1979 just months after a string of bloody attacks on the British by the IRA.
Correspondence between the Irish embassy in London to Dublin highlighted the anti-Irish bitterness in the UK at the time, with popular opinion accusing the Irish Government of being soft on security and harbouring the IRA.