The Government has told Telecom to improve the 111 emergency call system, which has had several partial failures this year.
Two independent reports have identified problems with the system.
Communications and Information Technology Minister Steven Joyce says the letter asks Telecom to work urgently and closely with the Government to develop a comprehensive agreement.
The reports found problems with infrastructure, governance arrangements were unclear and there was a failure to keep pace with mobile phone technology.
Mr Joyce says roles should be set out for Telecom, the Government and other players in the industry.
He says the agreement should contain a comprehensive set of performance measures and plans for managing situations when performance is below expectations.
Telecom says it has already made improvements to the system and the public can rely on 111.
