It will become increasingly difficult for police to recruit informers if their identities are revealed by inquiries, Sir Hugh Orde has said.
Sir Hugh Orde has raised concerns about infromants coming forward
The PSNI chief constable said this could have serious inplications for both the fight against international terrorism and organised crime.
Sir Hugh said if people were not confident their identities would be protected they would not come forward.
He said those exposed as informants remained under real threat in NI.
Speaking on BBC Radio 4, Sir Hugh said: "Are people going to say 'I am confident that I can tell police officers about something which is hugely sensitive and if ever it is exposed I am dead?'
"I think they are going to step back and that critical piece of information that can provide the wider picture around all the other information we are gathering from other ways could be missing."
He said this could lead to a tragedy.
Sir Hugh said he was not opposed to inquiries and would help them as much as possible.
"My concern is the legislation as currently framed means I can't protect - and can't tell people I can protect them - from exposure 10, 15 or 20 years down the line."
However, Paul O'Connor of the Pat Finucane Centre, rejected Sir Hugh's comments.
"The names of informers have not been made public," he said.
"They are made available to a tribunal of inquiry, at which point it is virtually certain that those people would then make a legal application for anonymity, which would be granted."