"It is a career opportunity to these people. They show up everywhere."
Mr Barnes said the pair were both using European betting sites.
"On some of these European betting sites, you can bet, for example, on a first serve whether a guy is going to make a fault or not. Somebody sitting in the stands with a cell phone can transmit this information to somebody in Europe and that somebody can bet that the first serve is a fault. The person that is making the bet would have the information before anybody else so they are cheating in that respect."
Mr Barnes said the ATP were trained to spot anyone who might be illegally betting. "Most of the time it is pretty obvious. Everybody in the stands is standing up and applauding and one guy is sitting there with his hands in his pockets."
TAB spokesman John Mitchell said his agency had nothing to do with the illegal betting.
It was most likely an unrecognised company, or a private booking agent, spectators were using.
"It's illegal, of course, but there's nothing to stop people from starting their own private books. But they'll get caught and they'll get stung."
Mr Mitchell said spot-betting was when bets were made during a match about different points in the game.
"You'll have these, usually illegal, betting operators that will allow people to place bets on 'This guy's about to serve a tennis ball, I think the first serve will be a fault' - that's kind of back-alley, down at the pub, dodgy book-making really."
The Tennis Integrity Unit is investigating both incidents of illegal-betting - the body has been at both tournaments held at the ASB Tennis Centre over the past fortnight.
The unit is charged with enforcing the sport's zero-tolerance policy towards gambling-related corruption worldwide, and it applies to all players and personnel associated with tennis.
It was formed in September 2008 as a joint initiative of the International Tennis Federation, the ATP, the WTA and the Grand Slam Committee.
