Pokie grants to amateur rugby had increased from $9 million in 2005 to $29 million in 2008, raising questions over the sport's reliance on grants, Problem Gambling Foundation chief executive Graeme Ramsey said.
"How can we allow a situation where our national game is dependent on this level of funding?"
Since 2005, rugby was the main recipient of pokie grants with $108 million, followed by horse racing ($87 million), football ($49 million), cricket ($39 million) and netball ($29 million).
More than 860 rugby organisations have received pokie grants since 2005, with 13 rugby unions receiving the most.
The ORFU has secured more than $5.1 million since 2005.
The Canterbury Rugby Football Union ($5.3 million) and Waikato Rugby Union ($11.4 million) received more.
More than half of all poker machine grants to the Otago union, $2.98 million, came from The Trusts Charitable Foundation, which included the largest individual grant of $258,000 in 2007.
Earlier this year, the trust came under fire for its involvement with the racing industry.
ORFU business manager Neville Frost said pokie grants went towards "providing resources for amateur rugby throughout Otago".
Asked why so many grants had been given by the trust, Mr Frost said the union had built a relationship with the trust.
"Generally, trusts provide funding if they are confident that the funds are appropriately spent on worthwhile projects," he said. The union provided resources to more than 8100 amateur players and "gaming grants are critical if the union is going to provide resources to those players".
If that funding stream was cut, the ORFU would have to "seriously curtail its spending on amateur rugby", he said.
New Zealand Rugby Union community and provincial union rugby general manager Brent Anderson said pokie funding was an important source for funding amateur rugby.
Unions and clubs were their own separate entities, and were "independent when it comes to raising money and spending it, and the NZRU has no audit function over them".
The rugby union had no official policy in regards to poker machine money, but offered guidance to clubs in a manual which was issued in 2005-06, he said.
"We also stress the need to ensure absolute compliance to our provincial unions and have met with the major trusts seeking their views on how rugby organisations are operating and what the NZRU can do to assist," Mr Anderson said.
A Waikato Rugby Union spokeswoman said poker machine grants went towards all amateur coaching, refereeing and amateur representative programmes.
The Grassroots Trust distributed 55% of pokie grants to the union and other associated rugby activities within its region, she said.
The Southland Rugby Football Union ranked 13th overall for pokie grants, with $3.07 million since 2005.
North Otago Rugby Football Union is 54th after receiving $271,000 in grants.
The Otago club given the most was the University of Otago Rugby Football Club.
It received $262,000 in grants since 2005, the 58th most of the 869 rugby organisation that applied for grants.
