Mr Lunn was speaking after it was revealed the investigation into the army’s most high-ranking agent in the IRA would also examine possible crimes by IRA members, agents, army and police handlers.
Trevor Lunn MLA said: “It is vital to this investigation that no stone is left unturned in the search for the truth and that it is allowed to be conducted in a manner that upholds public confidence in the rule of law.
“This is an investigation independent of all of the agencies that may have had any interaction with the handling of Stakeknife, and those bodies should be on notice to co-operate fully in line with both the letter and the spirit of the terms of reference.
“I note that this investigation could take up to five years with an estimated cost of £30m. Indeed, that estimate could change considerably as it unfolds. The indication is that this cost will be borne by the PSNI. The Executive urgently needs to secure financial cover from the UK Government to avoid a financial trade-off with the policing of the present.”