The ACT auditor-general has urged caution in relying upon the Territory Government's cost-benefit analysis for its billion-dollar light rail project.

The Government has finalised contracts for the plan, which it claims will deliver $1.20 in benefits for every dollar spent.

However an auditor-general's report released today urged caution in using the figure, saying the transport benefits alone that the project would deliver were just $0.49 for every government dollar.

Auditor-general Maxine Cooper said the Government's cost-benefit figure, which incorporates wider economic benefits associated with the project, needed to be used with caution.

"There is a lack of an agreed methodology and robust data in Australia for calculating wider economic benefits," she said.

"In the $1.20 benefit-cost ratio approximately 60 per cent of the project's benefits are not transport related.

"This is large compared with other transport infrastructure projects."

Dr Cooper recommended that a benefits realisation plan be implemented to ensure the projected benefits came to fruition.

"Realising the project's benefits will involve a wide range of activities," she said.

"While some actions have commenced to realise benefits, without a benefits realisation plan there is a lack of transparency and accountability."

Minister concedes he did not read report

After the report was tabled, Planning Minister Mick Gentleman visited a construction site to spruik the increase in land values that light rail would bring.

"You see more people wanting to live on a corridor that provides good public transport," he said.

However when questioned about whether the Government had oversold the broad economic benefits of the project, it became apparent he had not read the report.

"I haven't seen the auditor-general's report this morning," he conceded.

Minister for Capital Metro Simon Corbell defended the Government's figures.

"The Government has always been very clear about the Capital Metro project, it's not just a transport project," he said.

"It's a city building project, it's about changing the way land use ... happens in our city.

"We want more people to live close to high-quality public transport, and building light rail drives that behaviour change about where people choose to live."

Opposition slams Government figures

However Opposition transport spokesman Alistair Coe said the auditor-general's report proved the Government's figures were "rubbery".

"With regard to the benefits, she says they cannot be substantiated, all that we do know is that for every dollar invested, we're only getting 49 cents back in terms of transport benefits," he said.

"The rest is very, very rubbery.

"All that we need to do if we want density on the Northbourne corridor is for the Government to sell blocks of land.

"We don't need light rail to spark investor interest in building apartments on Northbourne Avenue."