The Security Service will only remain in Northern Ireland as long as the threat from terror groups exists, Matt Baggott has insisted.
The PSNI chief constable acknowledged that some nationalists still view MI5's presence with suspicion, but he claimed it is only in the region to keep people safe and he made it clear that he remains in operational control of security operations.
"In terms of national security there is a Security Service still here but, you know something, all I've seen from them is a desire to keep people safe," he said. "And if this problem wasn't here they wouldn't be here, and I wouldn't want them here."
He added: "We (the PSNI) have operational control and they (the Security Service) are required to show us the information and intelligence and I have seen no signs that that is being broken.
"So the Service has expertise and it has a role here under part of the devolution of policing and justice, and that's accepted by everybody. They are here simply to keep people alive, but I am in control operationally and no-one dictates to me what I do."
Mr Baggott said the Service is playing an important role in the fight against dissidents.
"In terms of the way intelligence is being managed, the way it's being turned into operational intervention and bringing people to courts, all that is subject to due process," he added.
"In the longer term, if we didn't have a terrorist problem we wouldn't have the Security Service here and I think you have to put the onus for that back on to the public and back on to people here to continue to fight, to persuade and remove these people (dissidents) from the equation. Then we could spend the money on hospitals."
He said he is aware that MI5 is still viewed with mistrust by some people in the region, but added: "I do see that but I have to live with the facts: everything I've seen has been just simply about keeping people safe.
"I respect people's views on what it should look like, but we wouldn't be having this success (in operations against dissidents) if we weren't working closely with our friends in the south (Garda) who also work alongside the Service. There is a role (for the Security Services) here and I am accountable for what I do operationally."