Police have apologised today for a system failure that led to the emergency 111 line being down for almost two hours.

The fault was nationwide and appears to have affected callers trying to get through between midnight and 12.45 on Sunday morning.

Callers received an automated message saying the system was overloaded and could not proceed any further.

Police scrambled to rectify the problem, putting all available staff on the phones until the backlog was finally cleared at 2AM.

Acting national manager for Communication Centres, Inspector Mal Schwartfeger says a software failure is believed to be the cause.

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He says the fault was of great concern because of life-threatening situations that may have been compromised.

"What we're trying to do is get to the bottom of what actually caused this particular issue, and then we'll be making sure that it doesn't happen again."