A company that carried out significant coastal erosion work to a cliff-top waterfront home without consent has been fined $41,000 for "thumbing its nose" at the regulatory process.

The Auckland Council is urging waterfront residents dealing with coastal erosion threats not to take matters into their own hands.

The Beachlands homeowner decided to carry out preventative erosion work by building a huge retaining wall at the Hawke Cres property without resource or building consent, landing himself before the Environment Court this year.

Auckland Council prosecuted K4 Group Management Limited for illegal use of the foreshore. The company pleaded guilty and was fined $41,250.

K4 Group Management is owned by Ranjit Keshvara, according to Companies Office records, who also owns the property.

The unconsented work involved the construction of two 20m-wide retaining walls, one 5.8m high and another 4m high. Rocks, aggregate and concrete barriers were also placed on the foreshore to provide access and a working platform for machinery.

The council pointed to rules restricting the deposition of material in the coastal marine area unless resource consent is given.

"Both properties, in this case, are identified in the Auckland Unitary Plans maps as being within a coastal erosion hazard area and in that area works in the vicinity of coastal cliffs generally require resource consent as a discretionary or restricted discretionary activity," a spokesperson said.

The council reminded coastal property owners that under the RMA, the Auckland Unitary Plan contains rules relating to activities on land and in the coastal marine area, which includes the foreshore.

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Construction including two 20-metre-wide retaining walls was put up at the Beachland property. Photo / Supplied

"We understand that protecting properties from erosion is important, but we ask homeowners to work with us and apply and gain consent before starting any work," council investigations team leader David Pawson said.

At the sentencing, Chief Environment Court Judge David Kirkpatrick said the regulatory regime existed for good reasons.

"It is in place to protect the environment and the health and safety of the public.

"The owner's decision to proceed in the expectation he could obtain the necessary consents retrospectively amounted to a thumbing of the nose at the regulatory regime." Kirkpatrick said.

Pawson said the company's sentencing should act as a deterrent to others who were considering doing work to their properties that merge onto any areas of coastal or council reserves.

"The damage to the area can cause major issues, and owners have an obligation to understand the rules pertaining to their property."

- Ellen Thompson, Open Justice