The Queensland Government has unveiled plans to build a $5 billion dual bus and train tunnel across 5.4 kilometres of Brisbane’s CBD.

The Government led by Premier Campbell Newman announced the massive project over the weekend, which will see a split-level tunnel dug with a station at Woolloongabba for sporting events, a stop along George St to drop people at the new entertainment and casino precinct, and a third terminal near the busy, above-ground Roma Street Station.

It is scheduled for completion by 2015.

There have been understandably mixed reactions to the plan intended to ease traffic on bridges and other inner-city roads. The currently-named Brisbane Underground plan combines two previous ideas, hypothetically saving about $2 billion by merging the previous Labor government's Cross River Rail project and the Brisbane City Council's Suburbs 2 City bus plan.

Lobby group Rail Back on Track described the Underground Bus and Rail Tunnel (UBAT) plan as an exciting project, which will be welcomed by members.

Rail Back on Track spokesperson Robert Dow says it must be done properly.

“Future proofing is essential, there will be only one chance to get it right,” Mr Dow said.

“For example, new rail stations should be constructed in a space to allow nine car trains, and the bus tunnel segment must be of such size to allow rail or light rail modifications down the track.”

National industry group The Tourism and Transport Forum chief executive Ken Morrison said it would be a significant, world-first achievement.

“The two greatest transport constraints facing the Brisbane CBD are rail capacity across the Merivale Bridge and trying to cater for the predicted growth in bus numbers which, if nothing changes, will see more and more buses crammed into the limited space of Brisbane's surface road network,” Mr Morrison said.

“Instead of trying to solve these problems separately, the government's proposal addresses both of these issues in an innovative project that will attract worldwide interest.”

Queensland Opposition leader Annastasia Palaszczuk said the tunnel, which will require larger machines than were used on Brisbane’s most recent tunnel ‘ClemJones’, is a needlessly large strain on the state budget.

“I'm very concerned that a bigger tunnel will cost more money, and Campbell Newman and the Treasurer [Tim Nicholls] have not said where the money is coming from,” she said.

“I'm very concerned that this means one thing – asset sales.”

The Queensland Premier wants less talking and more digging.

“There's been too much conversation in the past,” Mr Newman said.

“But we are a government that promised to deliver better planning and infrastructure and that is what we are doing,”