Queensland's public transport fares could be slashed to 2010 levels by allocating money from the existing transport budget, the Greens say.

The party on Friday released an election proposal to spend $200 million from the state's existing $5.5 billion annual public transport budget on reducing fares by 55 per cent - the same increase commuters have seen over the past four years.

"It's disgraceful that it's so expensive," Greens leader Senator Christine Milne said at Brisbane's Cultural Centre Busway.

Senator Milne warned Queensland's bus network could be privatised under the Liberal National Party (LNP).

"(Premier) Campbell Newman wants to sell off the buses," she said. "But the Greens say we want to fill up the buses, we want to keep the buses running full - better timetables, cheaper fares."

Much of the cost of the policy would be recouped through increased patronage, lead Queensland spokesperson Dr Charles Worringham said.

"This is not just of benefit to the people who use public transport," he said.

"It helps everyone, other motorists as well, by reducing congestion on our roads, reducing the cost of wear and tear."

Ballooning public transport fares were to blame for huge declines in patronage, and the enormous transport budget could afford the hit, Senator Milne said.

She criticised Mr Newman and Prime Minister Tony Abbott for having an "obsession" with tunnels and motorways.

Commuters on the NewStart allowance would be entitled to concessions at a cost of four million dollars a year under the policy.

The Greens propose to spend $60 million on improving current bus, ferry and train timetables and would also commission a review of public transport in regional communities.

The LNP last year reduced public transport fares by 5 per cent and has frozen a 2.5 per cent increase which was due to start at the beginning of 2015.