Chief executive Ray Tame said the City was extremely proud of the quality of its North Forrestdale Development Contribution Plan Number Three.

“These new suburbs are the direct result of at least 15 years of hard work by the City to get the quality infrastructure you now see in Harrisdale and Piara Waters,” he said.

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“The scheme has been held up as a role model by the land development industry.

“While the two authorities will have to agree to the secession, I have never heard of a boundary adjustment being approved half way through a Development Contribution Scheme, particularly if the scheme had to be split.

“The City would oppose this of course, and there is likely to be considerable compensation to be discussed with the local government that assumes responsibility for the DCP.

“If indeed any boundary adjustment process is triggered by a petition, I would expect a long, arduous process before the two authorities involved came to an agreement on the outcome.”

Group spokeswoman Kelly Lacquiere was not surprised at the City of Armadale’s response.

“Initially this campaign was all about lower rates, particularly the excessive hikes the City of Armadale force on all suburbs within their catchment but also particularly on the extra costs associated with living within the suburbs of Harrisdale and Piara Waters,” she said.

“After speaking to members of the community and information garnered from our Facebook polls, it is clear we have a real disconnect with the City of Armadale.”

She said a very small minority used the main facilities offered by Armadale while the vast majority used Cockburn’s facilities.

“We want to be a part of the community we connect with and pay rates towards the facilities we use. That council is the City of Cockburn,” she said.

Ms Lacquiere said the group believed its strategy could show “without a doubt” that Harrisdale and Piara Waters belonged within Cockburn’s zone and the Local Government Advisory Board would make that determination.

Cockburn Mayor Logan Howlett said the City had not been contacted by the group, but was aware of the issue.

“Any boundary change proposal needs to be supported by all local governments involved in order to be successful,” he said.

“These changes must also form part of a larger and considered approach which promotes both long-term sustainability of local governments and better outcomes for residents.”

He said transition processes to make boundary changes were costly and time consuming. Cockburn was against the proposal before the advisory board to move its residents from Hamilton Hill and parts of North Coogee to the City of Fremantle.

Ms Lacquiere said if the group’s campaign was uncuccessful it would continue to closely question the City of Armadale’s expenditure.