Thin end of the wedge: Phil Mickelson will not use the controversial Ping Eye 2 wedge when he defends his Northern Trust Open title Photo: AP

The world No 2 came in for criticism at the Farmers Insurance Open last week when he played with the non-conforming, but PGA Tour-approved, pre-1990 Ping wedge.

The club at the centre of the row features 'U' grooves rather than the new standard of shallower, narrower 'V' grooves which reduce the amount of spin generated on the ball - a move introduced in a bid to emphasise golfers' skill over technology.

A legal settlement struck in the early 1990s left a loophole which means Ping's Eye 2 wedge can be used in the US, but three-time US Tour winner Scott McCarron said he was "appalled" by Mickelson's decision to use one at the Farmers Insurance Open.

McCarron went so far as to say it was "cheating", although he last night spoke with Mickelson and apologised for that remark.

European No 1 Lee Westwood also criticised Mickelson, saying the American was "bending the rules", and Mickelson on Wednesday said he would not use the club as a sign of respect to his fellow professionals, who rallied in support of him last season when his wife Amy was diagnosed with breast cancer.

"I like and respect these players out here and when my wife and I were at one of our low points, the players came together and did one of the nicest things that could have been done to show support and it meant tons for me," Mickelson said.

"Out of respect for them, I do not want to have an advantage over them, whether it's perceived or actual.

"So this week I won't be playing that wedge.

"My point's been made, I won't play it."

An angry Mickelson demanded that action be taken to close the loophole and also criticised what he perceived as a mishandling of the rule change's implementation.

"I have been very upset with the way the entire rule change has come about, and its total lack of transparency," he said.

"This has got to change. To come out and change a rule like this that has a loophole... is ridiculous.

"It hurts the game and you cannot put the players in the position to interpret what the rule means.

"This should have been decided well before this came out. It put me and it put all players in a bad spot and it needs to be changed."

Mickelson also warned that if action was not taken he would have no choice but to put the wedge back in his bag.

"If these governing bodies cannot get together to fix this loophole... then I will put the wedge back in play," he said.

Padraig Harrington was another player hoping for a clear signal from PGA Tour commissioner Tim Finchem regarding the issue, and said he may use the club at the Riviera Country Club tomorrow.

Harrington was waiting for Finchem's official verdict following the commissioner's meeting with PGA Tour players on Tuesday night.

But the commissioner today said there would be no instant solution and his policy board would be referring the issue to an independent committee for evaluation.

"Whether I'm going to use them or not, I'm kind of waiting to see what the Tour's direction is," Harrington said.

"I'm preparing myself for all eventualities. It would be naive not to.

"Every 10 minutes it's in the bag, it's out of the bag. That's basically how it's been going. I haven't settled at all on what I'm going to do, but I'll have to.

"It could be 10 minutes before my tee time and not know what I'm going to do this week.

"I'm hoping for some good clarification from Tim Finchem.

"I'm hoping something comes out... that takes the decision out of my hands."