First Greater Manchester plans to increase the price of onboard tickets by 10p in January but freeze the cost of those bought via its mTickets app.
It said it wanted to encourage customers to buy tickets in advance on smartphones to speed up journey times.
Passenger group TravelWatch NorthWest said it may reduce delays but penalised those without the technology.
A spokesman for the bus operator said about 15,000 passengers already use the app and its research showed boarding times would be 75% faster if all passengers used it.
He said the company were confident freezing ticket prices on the app would encourage more customers to pay that way.
TravelWatch NorthWest's John Moorhouse said while he understood it was "an incentive to use the app, a lot don't have the internet and rely on buying [tickets] on the bus".
He also said it was "unfortunate" for the 22% of passengers who do not travel with smart phones.
The majority of single onboard tickets will see a 10p increase from 2 January.
Passengers buying tickets onboard some Greater Manchester buses are to pay more than those using a smartphone app.