One of the operators of the Prime Minister's $50 million cycleway will charge mountain bikers for using public land to pay for the maintenance of the network of trails.
Bike Taupo will charge $40 for an annual membership to ride the Craters of the Moon tracks from January 1, using the money raised to fund the upkeep of the 90km stretch of New Zealand Cycle Trail it looks after.
The funding gap has emerged at other parts of the cycle network across the country after money was put forward to build the trails - but not to maintain it.
The Government is aware of the problem and says money will be sought to cover the gap in the Budget this year.
The trail came out of Mr Key's jobs summit in February 2009.
Originally devised as a Cape Reinga-Bluff track, it instead became a series of "Great Rides" the length of the country.
Bike Taupo chairman Rowan Sapsford said the organisation was among trail operators under financial pressure because of the cost of maintenance.
"Some tracks just can't maintain the level they are built at," he said. "The Prime Minister's budget is for the establishment of them but not the ongoing maintenance.
"It is a huge risk for a lot of the cycle trails that if there is not ongoing support they will fall over."
He said the group maintained a total of 250km of trails, which cost "six figures". Now, money earned by charging for access to the 80km-long Craters of the Moon trails, run on public-owned land, will go towards maintenance and upgrading the facilities.
The Commissioner of Crown Lands granted the group a 14-year permit to run the trails at $1 plus GST a year with extra charges for events.
The Craters of the Moon trails are popular, with track counters recording around 30,000 people a year along some paths.
Bike Taupo plans to close access to all non-members from New Year's Day. Memberships - and the right to access the trails - will be sold from $10 for a week up to $40 for an individual for a year. Members will be identified on the trail by tags showing they have paid.
Associate Tourism Minister Chris Tremain said the need for maintenance funding was understood and would be addressed.
"The $50 million that was originally appropriated was for the capital cost of building the trail. We are conscious of the fact there is going to need to be some form of ongoing funding for maintenance. We are considering that for part of Budget 2014."
Mr Tremain, who cycled part of the trail network with his son last week, said it had proved a huge success in attracting business to its route.
The Weekend Herald understands the patchwork way in which the trail was constructed has created patchy need for assistance. In some areas, council partnerships cover maintenance costs while in others the Department of Conservation does the maintenance when trails pass land they administer.
Green Party cycling spokesman Kevin Hague - who has been closely involved in developing the trail - said operators were meant to have considered maintenance when pitching for the contracts.