"Governments alter laws all the time to encourage economic activity to take place. So this whole sell-the-law thing is a Labour Party spin and you shouldn't buy into it."
The deal could allow Sky City to install up to 500 new pokie machines, but Mr Joyce said no numbers had been agreed while negotiations with Ministry of Economic Development staff were ongoing.
"They will come back to me at some point with a recommendation in terms of what the final arrangement should be, I'll then take it to my Cabinet colleagues," he said.
"We may not even have a deal. The reality is we are talking about a negotiation.
"It's quite possible that both parties end up walking away and saying we can't get what we want. That's an entirely possible outcome."
Mr Joyce said he would not put a timeframe on the negotiations.
The Sky City bid was one of five proposals to build the convention centre but the only one the Government was considering.
Mr Joyce said the proposal would not cost New Zealanders but there were other factors, including Sky City's central city location.
"There's a very good proposal out at Greenlane at the raceway, for example, but it's a long way from the CBD, it's a long way from the hotel stock, so for those reasons that one is very difficult to make fly."
Mr Joyce denied new pokie machines created more problem gamblers.
"The reality is this - gaming in New Zealand is well-established across a range of areas and most people cope with it very, very well."
Mr Joyce said if opposition parties had the courage of their convictions they would call for the casino to be shut down.
"Why not? Because they know it supplies 3000 jobs for New Zealanders."
The convention centre was an opportunity for New Zealand to claim more of the 8300 international conventions held around the world each year.
