Feyen said he had attended deliberations for the plan and heard all public submissions on it, but cited rates increases and council debt levels as concerns.
"Until I've been fully informed I have decided not to put my signature to this binding document," he said.
However, deputy mayor Wayne Bishop said the Long Term Plan was based on a prudent financial strategy that aimed to manage expected growth while living within means.
"A key aspect of the financial strategy is achieving a balance between loan and rate funding to maintain existing assets and purchase new ones," he said.
The plan is the culmination of a process of consultation and submissions and included three key challenges and two "community conversations", the council said.
The challenges included whether to sell off some of the district's community halls, the season length of Foxton Swimming Pool and how to handle water and wastewater infrastructure for growing settlements.
Decisions made in the plan for these challenges included selling off Foxton Memorial Hall and Coronation Hall while deferring decisions on three others, agreeing to extend the pool's season from five to eight months, and proceeding with feasibility studies for water and wastewater in Ōhau, and water for Waitārere Beach, but not for Waikawa Beach and Hōkio Beach. A study for Manakau was deferred until Year Four of the LTP.
The two "community conversations" looked at water sustainability and the need for a community centre in Shannon.
"On water sustainability, council will proceed with its proposed approach — installation of pressure-reducing values, detecting and fixing leaks, and continuous monitoring and condition assessment. Council will also look to establish a Horowhenua Water Working Party to consider water sustainability issues," Bishop said.
A feasibility study for the potential development of a Shannon Community Centre will be carried out in the 2019-2020 financial year.
A council media release about the plan said it would continue work on existing projects to maintain and improve levels of service and plan for growth.
The plan also includes a grant of almost $165,000 to the Foxton and Beach Bowling Club funded from the Foxton Beach Freeholding Account, as well as commitment to a feasibility study about stormwater discharges into Lake Horowhenua.
Thanks to an impassioned push by councillor Piri-Hira Tukapua at a previous council meeting, $5.5 million was allocated to years four to seven of the plan to help implement findings from the study into the polluted lake.
Some elected members weighed in on Thursday morning on the LTP adoption and the mayor's refusal to sign it, with one saying she was gobsmacked.
Victoria Kaye-Simmons said the council had undertaken the largest engagement process that Horowhenua had ever seen.
"For it to be undermined by the person who led the engagement on the day of the adoption of the plan is gobsmacking but thankfully a majority supported [it]," she said.
Cr Bernie Wanden said as a first-time participant in the process he was "more than satisfied" with the professionalism of council staff and the robust discussion which would ensure the plan gave the district a framework to look forward with positivity.
However, he said the re-evaluation of the Ōtaki to North of Levin (O2NL) expressway project by the NZ Transport Agency dampened his hopes for that positivity in the immediate future.
He also cited a lack of leadership from Feyen.
"[The mayor] would not support this plan and has put his own interests and his support of the new Government ahead of the interests of this community," he said.
Christine Mitchell said she was pleased with growth having an impact on rate increases, in that rates could be spread over more properties.
Jo Mason said it was "an absolute relief and highlight" to have the 20-year plan adopted.
Ross Brannigan said he was proud of the efforts of council officers and elected members, but was at a loss to explain the actions of the mayor and Cr Campbell.
"By not supporting the Long Term Plan they have further isolated themselves from our community," he said.
