Lord Reid told a Westminster committee some elements of the peace process were dealt with confidentially but stressed the administrative scheme that dispatched so-called letters of assurance, telling around 200 individuals they were not being actively sought by the authorities, was not one of them.
"I am not suggesting for a minute we advertised this, I am not suggesting for a minute we went out and made public statements about this scheme," he told members of the Northern Ireland Affairs Committee.
The Labour peer added: "We didn't do that, I admit that, but it wasn't kept a secret."
The politician, who also served as Home Secretary under the last government, was giving evidence to the committee's ongoing inquiry into a scheme that was thrust into public focus after the collapse of a court case against a man accused of the IRA's Hyde Park bomb.
The prosecution of John Downey, 62, from County Donegal, over the 1982 bomb attack that killed four soldiers was halted in February this year after a judge found he had been wrongly sent one of the letters in 2007, when in fact the Metropolitan Police were looking for him. The judge decided his prosecution had represented an abuse of process.
Mr Downey denied involvement in the attack.
The committee is also examining the wider scheme agreed between Sinn Fein and the Labour administration.
Unionists in particular have been fiercely critical of the process in the wake of the Downey judgment, claiming it was carried out without their knowledge.
Lord Reid, who was Northern Ireland Secretary from 2001 to 2002, said Northern Ireland Office (NIO) officials held secret meetings during the peace process, citing encounters with IRA members.