Commuters from Sydney's outer suburbs and regional areas will bear the brunt of increases in Opal public transport fares if the Baird government accepts the pricing regulator's proposals, the NRMA and other community groups have warned.

A rise in fares of between $13 and $18 a week for people in outlying areas travelling to Sydney's CBD would be higher than what they would face from a 0.25 per cent rise in interest rates on a $400,000 mortgage, the motoring group calculates.

The Independent Pricing and Regulatory Tribunal has proposed sweeping changes to the fare structure for the state's ticketing system, including an end to free travel after eight journeys in a week and a tightening of eligibility for the Gold Opal card.

A long list of community groups, councils, and politicians such as Opposition leader Luke Foley have taken aim at the proposals, arguing that significant fare increases will discourage people from taking public transport.