The Ministry of Health is defending the time it took to release the official Covid-19 contact tracing app.
It took between five and six weeks from when tech developers gave their ideas to the ministry, and in one instances a fully-built app, until the release of the official NZ Covid Tracer app.
Director-General of Health Ashley Bloomfield said in a statement the ministry considered the full range of options.
"We were looking to see what other countries were doing. We had many many offers of solutions."
It took time to ensure privacy, he said.
"When a government agency develops an app it is not the same as when a private app provider does so."
The ministry had to align the app with other government approaches and get Cabinet approval.
The decision to build its own app, with contributions from two tech developers was so the ministry could be confident about data security, and add further features, Dr Bloomfield said.
However, an industry watchdog in the UK, Proprivacy, gave New Zealand's app a score of one out of 10 for privacy in its comparison of pandemic tracing systems worldwide.
This is the same score as the Philippines and Norway, and one better than China's score of zero. Australia is rated 6 for its Bluetooth system.
"The way the app is set up ... could potentially open up those digital diaries of New Zealanders' movements along with their personal data to cyber-criminals or intelligence authorities," Proprivacy said.
It noted the Health Ministry's refusal to release the app's source code which would have allowed the industry to test it.
Professor Dave Parry of AUT has called for the code's release.
Tech developer Daniel Britten, one of two given credit by the ministry for contributing to the app, said the Covid Tracer app was useful for contact tracing and would get better with enhancements on the way.
The app had "a commendable, strong emphasis on privacy", Britten said.