He said while he was "concerned" about conditions within the offshore processing network, the Coalition did not want to encourage asylum seekers to risk their lives at sea.
Turnbull told Radio National's Drive program the Federal Government could not afford to take a backwards step on the issue.
"There will be no resettlement of the people on Manus and Nauru in Australia. They will never come to Australia," Turnbull said.
"Now, I know that's tough, we do have a tough border protection policy, you could say it's a harsh policy, but it has worked."
Turnbull had earlier told Sky News that any changes to any policy would be done in a "considered way" and would be made by Cabinet.
He said conditions within the two offshore processing centres in Papua New Guinea and Nauru could be improved.
"[Immigration Minister Peter] Dutton and I, and the Government, we are concerned about the situation on Manus and Nauru.
"We're concerned that people are detained there, naturally it is not an ideal environment, we are doing everything we can to encourage them to return to where they came and the Government is actively looking at means of resettling them, whether it is in PNG, or indeed in Cambodia or looking at other options.
"It is tough, but the fact is we cannot take a backwards step on this issue."
Shadow immigration minister Richard Marles said Labor had been calling on the Federal Government to improve the way the two detention centres on Manus Island and Nauru were run.
But he said Labor's position was that the facilities should remain open.
"What I can tell you from the point of view of Labor is that this is a difficult issue, we are deeply concerned about the fate of those people on Manus and Nauru, we're also deeply concerned to make sure that we don't see any policy changes which result in people dying on our borders again," he said.