A controversial $1.13bn stadium on the Hobart waterfront is likely to go ahead after a key crossbencher expressed her support for the project, hours before the decisive parliamentary debate got under way.

Bec Thomas, an independent member of the Tasmanian legislative council, revealed in a statement on Wednesday morning additional conditions provided by the government means she will vote in favour of the Macquarie Point proposal.

Her support now means, barring an 11th-hour backflip from a member of Tasmania’s upper house, the project is set to go ahead and will enable the Devils to enter the AFL in 2028.

“This has been the hardest decision I’ve ever had to make,” Thomas said. “For me, the question has been under what conditions could it possibly earn support. That’s why my support for the project is strictly conditional on economic, governance, design and community safeguards that seek to protect the welfare of Tasmanians.”

Thomas claimed to have secured a fixed cap on the state’s contribution to the project, additional independent oversight, more funding for grassroots sport and targets for local jobs as part of the project.

Thomas’s support tips the balance of the 15-member upper house towards the project, which is a condition of the AFL’s agreement with the Tasmanian government to give the state a licence to play in the national competition.

A concept design of the proposed stadium at Macquarie Point in Hobart. Illustration: PR IMAGE

Casey Hiscutt, another independent who has previously expressed support for the stadium, told ABC radio soon after Thomas’s statement that he would not reveal his vote until the debate in parliament, but he had secured confirmation from the government that any spending above what is currently budgeted will require approval from both houses of parliament.

“Obviously going into the election with a position meant that I’d need to have a high burden of proof to dissuade me from that position, there’s nothing that I’ve seen that affects that,” he said.

The stadium needs the votes of eight MLCs in Tasmania’s upper house, after already winning support of the lower house last month.

The independent-dominated 15-member upper house chamber has three representatives from each of the Labor and Liberal parties which support the stadium, but the president – Labor’s Craig Farrell – will not ordinarily vote.

With Thomas’s statement on Wednesday morning, six MPs have now made statements of support, while Hiscutt and another independent Tania Rattray have also previously been in favour of the stadium.

A final vote on the stadium is expected on Wednesday or Thursday.