Rail passengers face fare rises of up to a third to travel between regions in Wales with the withdrawal of the cheapest "walk up" train fares.
Arriva said it would review prices once again in the autumn
From 20 May, the equivalent ticket from Bangor to Abergavenny will go up from £49.50 to £66.20 - a 34% increase.
Politicians said Arriva Trains Wales' plans to end 'SuperSaver' fares were a "disgrace" and "unacceptable".
The company said it was offering "new attractive prices" for long distance travel and encouraging advance booking.
The franchise it operates in Wales and the borders is managed by the Welsh Assembly Government, which along with the UK department of transport, provides an annual subsidy of £140m.
The funding covers upgrading of the train fleet and subsidising certain routes.
Passengers buying SuperSaver tickets have been able to walk straight onto a train and travel relatively cheaply, apart from on Fridays and Saturdays in the summer.
Arriva said sales of the tickets had fallen by 21% over the previous three months.
Nevertheless, AMs believe the cost of buying the nearest equivalent ticket, the Saver, will come as shock to passengers.
The journey from Llandudno to Cardiff will climb 29% from £59.40 to £76.80 and a trip from Aberystwyth to Wrexham will rise 17% from £30.30 to £35.50
Welsh Conservative transport spokesman Alun Cairns warned the price changes would put people off using trains.
He said: "At a time when we are trying to encouraging greater use of public transport these sort of steep price rises are unacceptable.
"Commuters need every incentive to get out of their cars and onto comfortable, reliable trains. Sharply increasing the price of a ticket hardly helps achieve this."
North Wales Liberal Democrat AM Eleanor Burnham called the new prices "a disgrace" and said they demonstrated the weakness of the privatised rail structure.
"The whole set-up is a complete nightmare, we've got to have a look at the franchise to see what we can do.
"We need to ensure we're getting value for money".
Plaid Cymru transport spokesman Alun Ffred Jones said a detailed explanation of the prices was needed.
"These are massive increases, out of all proportion. For the increasing number of people travelling to and from Cardiff this seems unreasonable".
Labour, who are beginning talks with the Lib Dems and Plaid about forming the new assembly government, said Arriva had made a "commercial decision".
But a Labour spokesman said: "Labour intends to deliver its manifesto commitments for the people of Wales.
"We will make further improvements to the north-south rail links and Valleys Lines. Labour will also deliver on introducing a scheme of discounted rail fares for older people."
Arriva commercial director Mike Bagshaw argued the new ticket prices were responding to changes in the market place.
He said: "Arriva Trains Wales new fare structure reflects the way people buy their rail tickets these days.
"For longer journeys people tend to book in advance which is why we have introduced cheap options for north to south travel such as from Bangor or Llandudno Junction to Cardiff from as little as £15 or £9.90 for railcard holders."
A company spokesman added that it would be reviewing its prices again in the autumn.