The Wellington Regional Council is considering banning bicycles on some of its new trains at peak times.
About 80 cyclists a day take the train at peak times to and from Wellington station.
The council says there needs to be enough room for passengers, as well as babies' buggies or wheelchairs, which must share the designated space with bikes.
One possibility, it says, is letting people take their bikes on the trains as long as they do not get on or off at the main Wellington station.
Cycling Advocates Network spokesperson Patrick Morgan says the council consulted the group but has broken a promise to cyclists.
Mr Morgan says a blanket ban in peak hours would be unduly restrictive and cause more people to take their cars instead of using the train.