"The likes of Kalyn Ponga have also turned, [and] Jordan McLean - he's a Whakatane boy from way back.
"I don't think they're actually playing for money but it's a good incentive. They just want to play in that competition which also puts them in with a very good chance of playing for Australia.
"It is a recruit-ment tool. It's disappointing that Australia have had to go that way to attract players."
McGahan's frustrations have come to a head in the wake of Jason Taumalolo and fellow former Kiwis David Fusitu'a, Manu Ma'u and Sio Siua Taukeiaho choosing to play for Tonga at the upcoming World Cup.
Kangaroos forward Andrew Fifita has also made the controversial switch to play for Tonga but can potentially still pull on a New South Wales jersey again in the future - as dual Australian-Fijian representative Jarryd Hayne did this year after returning from a stint playing in the NFL.
McGahan blames Australia for further reducing New Zealand's ability to retain their best players - by pushing for league's international eligibility laws to be relaxed, to allow players who qualify for more than one country to play for a tier-two nation.
"That whole eligibility rule has been driven from Australia," he said.
"It has damaged the international game. People are looking at rugby league and saying 'you guys are kidding'.
"It's a farce if you can pick and choose who you play for. It just makes us look silly.
"And I know that the International Rugby League Federation want to have a quality tournament but it's detrimental to the tier one teams because players who are eligible for tier two can pick and choose who they go for.
"Until that changes or there's some clarification and some definition of what eligibility is, then we're going to continue to have this."
McGahan acknowledges that Origin is the highest standard of football in the world - but argues if Australia are serious about involving the best players, then the annual interstate series should be opened up to include New Zealand and England players.
"You don't think James Graham or Sam Burgess wouldn't be a fair chance of making State of Origin? Or Jesse Bromwich?
"If you want to have the best players playing State of Origin, open it to everyone, and not just those who you want playing for Australia."
Taumalolo: I'll do talking on paddock
Kiwis defector Jason Taumalolo will do his talking on the field.
Kiwis captain Adam Blair and former captain Benji Marshall have taken swipes at the North Queensland Cowboys lock since his decision to turn his back on the Kiwis to play for Tonga at the Rugby League World Cup.
He gave coach David Kidwell barely 48 hours notice of his choice.
Born in Auckland to Tongan parents, the 2016 Dally M Medal co-winner said he chose Tonga to help develop the game in the Polynesian nation.
And, having arrived in Nuku'alofa on Thursday for a pre-Cup visit, he gave short shrift to the likes of Blair and Marshall.
"Obviously I've caused a bit of media stir and all that, but at the end of the day, I'm here to play for my country and I'm looking forward to doing that," Taumalolo said.
"Everyone's entitled to their own opinion. Everyone's entitled to say what they want, but at the end of the day it doesn't bother me - I tend to leave all the talking on the field.
"I wish in some way we could take the field soon, but I guess I'll have to wait until we come across them on the battlefield."
Taumalolo - whose arrival in the Tongan capital was delayed by 24 hours due to an overloaded flight - said he was doing his parents proud by playing for Tonga.
Other players including Manu Ma'u and David Fusitu'a have also elected to represent Tonga rather than the Kiwis, making them a credible World Cup contender. Tonga's World Cup opener is against Scotland in Cairns on October 29.
- additional reporting AAP
