The Labour Party is accusing the Government of misleading the public over the Sky City convention centre deal.
Budget documents reveal that if the plan goes ahead, taxpayers will contribute up to $2.1 million to ensure its design and facilities meet Government expectations.
Labour's economic development spokesperson David Cunliffe says Prime Minister John Key and Economic Development Minister Steven Joyce have continually claimed there would be no cost to the taxpayer and now the public is finding out there would be.
He says that is how the Government has justified working with just one party - Sky City.
Mr Cunliffe says the money is coming out of economic development areas like export and start-up company assistance and regional development.
The Prime Minister, however, is defending the budget allocation of millions of dollars towards a potential Sky City convention centre.
John Key says he has always said his preferred position is that no taxpayer money would be spent - and that if it does go ahead, it will have economic spinoffs.
The international convention centre deal is the subject of an Auditor-General's office inquiry, which is looking into the tender process.