Passenger train services in Wellington could be cut drastically if something is not done about the rail network's chronic underfunding, the regional council says.
In a new report, Greater Wellington Regional Council (GWRC) said there was a billion-dollar shortfall in funding for the capital's rail network.
The report also identified a significant backlog of maintenance renewal programmes that KiwiRail has to deliver in the region.
Council chair Daran Ponter said chronic underinvestment and inaction on rail renewal threatened to cut train services in the next one to three years.
"We are going to get to a point, relatively soon, where we are advised by KiwiRail that we cannot run as many trains, we cannot run them as fast as we would like, etcetera, and that will have a chilling effect on the network," he said.
"If some of the funding can't be found in the next few months, KiwiRail has warned of a growing risk that passenger services may be forced to operate on a reduced timetable."
The report said cuts to peak weekday services would amount to one train an hour on the Johnsonville line instead of three, two for the Hutt Valley instead of six, and three for Kapiti instead of seven.
There would be no Melling trains and greatly reduced stabling and servicing.
Ponter had written to government ministers on the issue.
Transport chair Thomas Nash said those cuts were a "worst case scenario" and there was still time to avoid such an outcome.
"There's a lot that can be done now to address the situation before it's too late."
Nash said ballooning insurance costs - which had jumped from $2 million per annum in 2018 to $11 million in 2023 - were also hindering the Wellington rail network.
GWRC was calling on the government to address how unaffordable insurance had become for the rail network.
It also wanted it to help address the expenditure shortfall.
KiwiRail on council contributions and upgrades
In a statement, KiwiRail chief capital planning and asset development officer David Gordon said the renewal programme in Wellington was estimated to exceed $1 billion, but he believed this could be dealt with over time.
"We are working with government agencies and GWRC on options to address this backlog.
"Councils have a contractual commitment with KiwiRail to contribute to the cost of maintenance, renewals and the operating costs of the Wellington and Auckland metro networks - based on their use.
"KiwiRail has been spending GWRC's contribution in Wellington on the highest priority works to ensure commuter services continue running smoothly."
They were undertaking upgrades, which could help to address the pressure of renewals, Gordon said.
This included double tracking a section of the Hutt Valley Line, enabling express style services to Plimmerton, replacing the old timber overhead infrastructure with steel, and progress on the rebuild of the tracks inside the two tunnels on the Wairarapa Line.
Insurance costs, which the council contributes to and are considered part of operating the network, have increased significantly in recent years, Gordon said.
KiwiRail said it would welcome a review into issues around council contributions and funding of metropolitan rail networks.