Metlink has confirmed fares for people aged under 25 will return to full price in the Wellington region.
It follows the government's decision to withdraw funding for age-based concessions.
The previous government's age-based concessions were introduced to Metlink services in September, including free travel for children under 13 and half-price travel for people aged 24 and under.
From 1 May, Metlink said people aged between 17 and 24 would return to full price, unless they qualified for an alternative tertiary or Community Connect concession.
However children aged between five and 16, or older if still at secondary school, would pay half the adult fare, and children under five would continue to travel for free on all services.
Transport committee chair Thomas Nash said the change would be felt by young people and whānau across the region, who were already struggling with the high cost of living.
"I don't want to end these concessions - we know they have made a big difference to people," he said.
"We want to maintain existing services and reliability, but we just can't afford to cover the cost of the concessions ourselves if we want to grow the network, especially with uncertainty around public transport funding from the new government.
"At more than $10 million per year, it would require an additional rate increase beyond the 19.8 percent we're currently proposing for the regional council."
Greater Wellington councillors recently confirmed the concessions would not be extended with council funds.
However half-price off-peak fares would still apply to most services, and concessions for tertiary students, Community Services and Te Hunga Whaikaha Total Mobility card holders would also remain.
Fare changes would automatically apply to Snapper cards.
Metlink encouraged all passengers, especially parents and guardians with children under 13, to make sure their card balances are topped up before the 1 May.
Other public transport authorities across New Zealand are expected to be making similar changes to fares and concessions.