The PSNI Chief Constable will give as much information as possible about the Stormontgate affair to the Taoiseach when they meet tomorrow.
Sir Hugh Orde will confirm that records of conversations Mr Ahern had with prime minister Tony Blair were among documents recovered by detectives investigating an alleged spying operation at Stormont.
Speaking to The Irish Times, Sir Hugh said the hundreds of pages of documents included what the PSNI calls targeting information.
"This covers details of police officers and prison officers. Also there were notes of conversations between Britain and the United States, notes on actual conversations - the actual official record of those conversations between the president [ of the US] and the prime minister and the Taoiseach and the prime minister." He said the documents included notes on "other political parties", though not on Sinn Féin.
Denying republican allegations that the Stormont raids were part of a wider political conspiracy designed to bring down a legitimate government, Sir Hugh added: "We would have been a lot more sophisticated than that. We wouldn't have left [ the documents] under someone's bed. We would have put them somewhere far more damaging."
He said the authorities would not have gone through the charade of warning hundreds of people and spending £35 million rehousing them.
"We would have been a lot cleverer around all this. The notion that this is some sort of conspiracy, well, it's a pretty poor conspiracy in that no one was convicted. The fact that we have complied utterly with the rule of law is the reason that we have not got prosecutions."
Agreeing with the dropping of charges against Denis Donaldson, Ciarán Kearney and William Mackessy, Sir Hugh said the Director of the Public Prosecutions Service had no option other than to retract the case against the three men originally charged in connection with the alleged Stormont spying affair.
"There comes a point when the public interest in law must succeed over a desire to prosecute an individual," he said.
Unionists remained unhappy last night following Sir Hugh's remarks. Sir Reg Empey, the UUP leader, and DUP MP Nigel Dodds are still critical of the handling of the affair. Sir Reg said he was no nearer to getting the answers he wanted after meeting Northern Secretary Peter Hain yesterday.
Mr Dodds welcomed Sir Hugh's "strong confirmation of IRA-Sinn Féin involvement in a spy ring at the heart of government". But he added: "Sir Hugh Orde has not explained why, given the clear evidence of criminal activity, no one is to be prosecuted for any offence whatsoever."
Sinn Féin said Denis Donaldson, unmasked last week as a spy, was an agent of the British state, not of republicans.
"He was not acting on behalf of republicans or our peace process agenda," said North Belfast Assembly member Gerry Kelly.
Sir Hugh said he could not comment on who was and who was not a covert human intelligence source". He also rejected Sinn Féin charges that the PSNI was involved in political policing, claiming: "We would not have caught our own source."
Policing Board chairman Sir Desmond Rea said last night he was satisfied there was no political policing in relation to the Stormont affair.
He said: "Back in 2002 the board held the Chief Constable to account over the Stormont searches . . . In respect of recent events, the revelations of the last week and the claims of Sinn Féin do not square up."