The $750 million price tag for a proposed new stadium linked to Tasmania’s bid for an AFL team was a “ballpark” figure estimated without a defined project scope, documents reveal.

The island state is pushing to become the league’s 19th franchise, with a vote of the 18 club presidents to be held in August.

Former Tasmania premier and treasurer Peter Gutwein in March unveiled a plan to build a stadium at Hobart’s Regatta Point he said would cost “in the order” of $750 million.

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He said the new facility, a recommendation of the state’s AFL bid taskforce, would be subject to stakeholder consultation, planning approval and Tasmania achieving an AFL licence.

Documents obtained under right to information by the state Labor opposition show the Liberal government received advice from sports development agency Waypoint about a week before Gutwein’s announcement.

The email from Waypoint put the total stadium cost at $747.5 million, but noted “site specific costs” had not been included.

“The location will require major civil works and piling over the water which is way beyond any site specific costs included for the benchmark projects,” the email reads.

“I reiterate this is ballpark cost advice! I hope this helps.”

In providing the price tag, the company notes there is “no design, no site information and no defined scope at this stage”.

Gutwein, who has since left politics and been replaced as premier by deputy Jeremy Rockliff, said the Liberals would seek funding from all levels of government, plus private sector involvement and equity raising.

He envisaged a two-year time frame for planning and approvals and up to three years for construction, saying the multi-purpose roofed stadium could be ready by 2027.

In last week’s state budget, the government committed $1.25 million to progress stadium feasibility assessments.

A scope for assessments, such as geotechnical and cultural surveys, is under development to go to market early in the 2022/23 financial year, the government says.

State Labor leader Rebecca White has labelled the stadium plan reckless economic management, saying it should be abandoned.

Senior government minister Roger Jaensch described the project as “a vision” with a “reasonable estimate at the time”.

“We had to be able to explain to Tasmanians what it could cost, now we need to go and do the work to find out what it will cost if we proceed,” he told the ABC.

The taskforce is ramping up community support ahead of the August vote and recently launched a campaign website.