The International Rugby Board today defended its desire for a 5km-wide ban of advertising claiming to be linked to the Rugby World Cup around stadiums for the 2011 tournament.
It said telecommunications and soft drinks companies were among those likely to try to exploit the event's popularity if law changes were not put in place.
And the IRB said legislation outlawing "ambush marketing", which is being considered by Parliament, was vital for the tournament's financial success.
Ambush marketing is the practice of companies not officially tied to an event using it to promote their products.
Any ban would not affect adverts not claiming to have any link to the Rugby World Cup.
The IRB's general counsel Darren Bailey said: "Ambush marketing is not a victimless crime. It affects rugby stakeholders around the world."
Curbs were needed to stop sophisticated marketeers who would seek to capitalise on the event's reputation, he said.
Mr Bailey, who appeared today before a parliamentary committee, said the IRB was responsible for "nurturing" and developing the sport globally by increasing participation, promoting competition and raising revenue for reinvestment.
The Rugby World Cup was its principal basis for doing so, he said.
The legitimate sponsors of the World Cup needed to be protected from those organisations which would seek to profit from the game and the event "without making an appropriate level of investment in the future growth and expansion of the game", he said.
Mr Bailey refused to name and shame companies which use "ambush marketing" but said he would provide written examples later.
Labour MP Maryan Street said Telecom had run a campaign that would have fitted what the IRB was talking about.
Committee chairman Gerry Brownlee said the committee needed answers because the IRB's desire for a 5km exclusion zone around World Cup events in New Zealand could impact on local businesses.