About 29,000 properties zoned single house and mixed housing suburban were in the areas considered by the appeals.

Homeowners in some of Auckland's leafiest suburbs have been left "in tears" after finding their streets re-zoned to allow for densification.

The High Court has ruled the panel that considered Auckland's controversial Unitary Plan acted lawfully in reaching its decision allowing increased density in residential housing in certain areas of the city.

The court on Monday released its finding on 51 appeals and judicial review applications concerning the plan.

About 29,000 properties zoned single house and mixed housing suburban were in the areas considered by the appeals, including properties in Mt Albert, Glendowie, Blockhouse Bay, Judges Bay, Grey Lynn, Takanini, Howick and Parnell.

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A central issue for many of the appeals was whether the recommendations made by the Independent Hearings Panel (IHP) on the Unitary Plan were within scope of the submissions.

If they were not in scope, then affected parties would have the right to appeal any council decisions based on the recommendations.

In its 143-page decision, the court found the panel's approach to scope for residential zoning in the key test case areas was lawful.

The court ruled that the IHP had approached the matter correctly, with the exception of two test cases – one in Parnell and one in Takanini.

In his decision, Justice Christian Whata said: "The purpose of resolving the test cases was to provide affected appellants with guidance on the issue of scope. It will be for them to decide whether and to what extent they wish to pursue their appeals in light of my decision."

Character Coalition chairwoman Sally Hughes was disappointed in the decision.

The coalition is an umbrella organisation representing 67 different groups committed to protecting Auckland's heritage.

But they did not represent all the 29,000 property owners affected, many of whom had contacted them "in tears" after learning of the rezoning, she said.

"Many people didn't even know this was taking place.

"We had distraught calls from people saying we had no idea, we live in a street of 100-year-old villas and now we could get apartment blocks across the street."

The coalition was not against intensification and believed many parts were in desperate need, but were opposed to destroying Auckland's most beautiful streets.

Homeowners were given little change to voice their opinion after the provisions were introduced towards the end of the process.

Hughes said the appeal process had been fair, but the coalition would continue to campaign to raise awareness about protecting the city's heritage.

Youth group Generation Zero campaigned for intensification, claiming it was needed to help fix the city's broken housing market.

Auckland spokesman Leroy Beckett said the court decision was great news.

"It's really good, they had their day in court, now we can get on with the other aspects of fixing the problem."

These included training more builders and addressing social housing needs.

The group was not opposed to protecting heritage, but believed there were adequate measures in the Unitary Plan to protect worthy buildings, he said.

Some "tough decisions" would have to be made, but blanket protection for all houses that would protect poorly built, cold 1940s buildings was unnecessary.

Auckland Council's Director Legal and Risk, Katherine Anderson said: "As the decision has implications for appeals that are still before the courts, the council will not be making any further comment at this stage."