A survey with a low number of respondents and high margin of error, showing that Rugby World Cup visitors spent up to $340 million last year, has been criticised as not credible.
The Ministry of Economic Development (MED) survey polled 250 people and has a margin of error of plus or minus 20%.
The ministry says these spending figures are the only ones the Government will have when it makes decisions about future major tournaments.
It accepts there is a high error margin, but tourism research and evaluation manager Peter Ellis is confident the figures are based on sound information.
But the head of the Tourism Department at Otago University, Professor James Higham, says it's difficult to attribute tourism benefits to a single event such as the World Cup; and the survey's high margin of error makes that task even harder.
Labour Party economic development spokesperson David Cunliffe says the high margin of error makes the survey results worthless.