Mr Key's figure is based on the drop in the number of pokie machines in non-casino venues nationwide over the past year. But across the seven districts that make up the Auckland Super City the decrease was just 23.
Based on present tallies of gaming machines in pubs and clubs, an additional 500 machines at SkyCity would return pokie numbers across Auckland to a level not seen since 2006. A rise of 350 would take numbers back to 2008 levels.
Mr Key said there was no guarantee that a deal with SkyCity would increase gaming machine numbers in Auckland. "It might be that there's no change in Auckland, it might be that there's still less in Auckland."
The Auckland Council has no overall policy on pokies but a spokesman said the previous seven local councils' policies would stay in force until they were reviewed as part of the Super City amalgamation work programme.
Those policies range from full sinking-lid policies in Manukau and Waitakere through to Franklin's open policy with no limits on venue and machine numbers.
The review of gambling bylaws is scheduled to begin this year with policy in place by mid to late 2013.
"I have always worked to minimise the harm from gambling," Auckland Mayor Len Brown said yesterday.
"That's why we had a sinking lid in Manukau and why I campaigned for one across Auckland."
However even under Manukau's sinking-lid policy, pokie machine numbers rose there in the year to March by 47 to 985.
Mr Brown has reserved judgment on the SkyCity deal until more detail is available. He said the Government could simply legislate for pokies at the casino if it wanted to but if the deal went ahead, he wanted it to include strong harm minimisation measures.
"I would expect these measures to form part of Auckland Council's final submission if the Government proposes any legislative change."
Mr Key yesterday said he did not know whether such measures were part of his Government's negotiations with SkyCity.
However, although Mr Brown's support for the deal was "certainly desirable", he did not think it was in question. "I've seen him on numerous occasions and I'm confident we'll get him over the line."