The State Opposition has slammed the Government for spending $300,000 on market research to see how people feel about proposed rises to public transport fares.

Documents tendered to NSW Parliament show in September last year, the government contracted PricewaterhouseCoopers (PwC) to carry out six weeks of customer research regarding the Opal ticketing system's public transport fares at an estimated cost of $310,000.

It was not clear what questions PwC asked of the public, but the State Government is set to overhaul the structure of train, bus and ferry fares under changes to be introduced in July.

Last year, the Independent Pricing and Regulatory Tribunal (IPART) released its proposal for the overhaul, saying 60 per cent of customers will pay less if the government adopts its suggestions.

But the Opposition's Transport spokesman Ryan Park said the devil was in the detail.

"IPART is saying most customers will save money; some of the savings they're counting are savings of two or five cents a trip," he said.

"That doesn't count when there are other customers who'll pay $900 extra a year."

Under the proposed changes, customers would be charged per kilometre so that fares for longer distances will increase.

IPART argued that was fair because at the moment, people who travel short distances are effectively subsidising those who make longer trips.

"People who live outside the inner city are usually on a much lower income than those in the city," said Mr Park.

"It has always been the case, just like it is with country hospitals, country roads that the main populations cross-subsidise and support to ensure everyone in NSW has access to fair and equitable public services."

He said IPART's proposed changes would mean people who travel from Blacktown to Central return every day will pay more than $900 extra per year, while Penrith residents will pay almost $700 extra per year.

"If the proposals are adopted it will be more cost-effective for many people to get back in the car," Mr Park said.

"That's not what we want to see."

The point is to make ticketing system fairer: Minister

But the Transport Minister Andrew Constance accused Labor of "scaremongering".

"They like to bang on about the rising cost of living, but the fact is when Labor were in office, public transport fares increased by 87 per cent," he said.

"IPART's draft report on public transport fares is exactly that - a draft."

Andrew Constance said no decisions have been made.

"The point of the IPART review is to make our ticketing system fairer, and the report needs to be looked at in its entirety," the minister said.

He also defended the government's decision to spend $310,000 on the market research about Opal fare rises.

"Engaging with customers is key to providing better services.

"This is part of our ongoing efforts to improve the system and deliver better outcomes."