Communities Minister Deirdre Hargey has admitted the new Casement Park development is set to cost around £110m.
The Sinn Fein MLA made the admission at a meeting of Stormont's Communities Committee on Thursday.
She had initially denied recent reports that the project was set to cost an extra £33m, calling them "not true".
However, she then told the Committee it would cost "about £110m", £33m more than the initial £77.5m budgeted for the project in 2012.
DUP MLA Jonathan Buckley asked the minister if the reports were true at the meeting.
"It's known that the budget has increased - we don't know the final figure yet because planning has not been granted, the application is still in the system," Ms Hargey said.
The GAA originally offered £15m as part of the project and earlier in February confirmed they would not be offering extra funding after costs escalated.
Mr Buckley asked if Ms Hargey agreed with the GAA's position that "no additional increase in their contribution is viable at this time".
The Communities Minister said the funding would be provided as an "80-20 split" but that discussions with the GAA and Finance Minister Conor Murphy were continuing.
Upper Bann MLA Mr Buckley pointed out that the GAA had annual revenues of "almost €74m" in 2019.
He said the public would be "shocked" by the £33m overspend and asked if the scale and capacity of the stadium could be reduced.
Ms Hargey blamed the increase on inflation due to the six year delay to the project and a 2014 High Court case following local objections, leading to new plans for a smaller ground.
Sinn Fein MLA Sinead Ennis said she was shocked to discover only one full-time planner was working on the planning application for the stadium due to the "size and magnitude" of the project.
She said that cynical people would "draw their own conclusions" about why this was the case and said people calling for the size of the stadium to be reduced had an "absolute lack of understanding" of the popularity of the GAA.
"I don't think that the quarter of a million Gaels across Ulster should be punished for the fact there's been no ministers to take those decisions," the South Down MLA said.
Ms Hargey said the Casement Park project was a priority for her department.
The Communities Minister said there would be no undue delay as the planning application was "moving at pace".
Ms Hargey said she accepted the stadium needs to be developed "as soon as possible".
In 2012 the government set aside £110m to cover the development of the dormant Casement Park along with Ravenhill and Windsor Park.
In January, Ms Hargey met with GAA officials at Casement Park to discuss future plans for the project.
An Ulster GAA spokesperson said that the organisation remained committed to the £15m offered to support the project.
However they said that the GAA would be open to further discussions with the Department for Communities around the issue when the planning is approved.
"We expect the issue to be resolved the same way any other public sector project would be dealt with by the department," the spokesperson said.
"Casement Park is a key priority for the Executive under the New Decade, New Approach agreement and we hope that the funding commitments will be met in the same way they were for the Irish FA with Windsor Park and the IRFU at Ravenhill."