Montgomerie lost four of the first six holes

The Scot now meets England's Paul Casey, who beat Canadian left-hander Mike Weir 5&3 at Wentworth.

The other semi-final will be between Shaun Micheel and Robert Karlsson.

American Micheel, who beat Tiger Woods in the opening round, won 4&2 against Luke Donald while Swede Karlsson saw off Angel Cabrera 4&3.

Highlights: World Match Play day two

Interview: Paul Casey

Luke Donald's iron masterclass

Montgomerie, champion in 1999, lost four of the first six holes to Michael Campbell but recovered to all-square after 18 holes.

That was thanks to putts of 15 and three feet for birdies at the seventh and eighth and two more birdies at the 14th and 16th.

If I had gone five down, then that would have been it Colin Montgomerie

Montgomerie twice went out of bounds on the front nine in the afternoon but recovered and the players were all-square going into the last of the 36 holes.

Both players found the same greenside bunker at the par-five hole but Campbell left his ball in the sand at his first attempt while Montgomerie managed to get up and down to clinch victory.

"He was unfortunate," said Montgomerie. "One of us had to play first and as I was two inches closer to the hole then it was him.

"But if I had had to play first I would have left it in the bunker as well. It is a new, very heavy bunker and he left it in there.

"I was four down before nine o'clock and that was not in the script - he got off to a flier. If I had gone five down then that would have been it, but three down is a different ball game."

It was a tough day for Donald, who was five down after 18 holes as Micheel had 12 single putts to go round in 65.

Someone's got to win this tournament and it might as well be me Shaun Micheel

The American was seven ahead two holes into the afternoon round and although he did begin to lose his putting touch, with three bogeys in five holes, it was too late for Donald to stage a fightback.

Micheel admitted that his win over Woods had given him the belief that he could pick up the �1m first prize.

"When you beat the number one player in the world you are brimming with confidence," said the 37-year-old.

"Someone's got to win this tournament and it might as well be me.

Casey, an impressive winner against Retief Goosen in his World Match Play debut, was behind three times to Canadian Weir over the first 13 holes.

The players went in level after 18 holes and although Weir again went ahead with 15-foot putt at the short second in the afternnon, the Englishman fought back and closed the match out on the 32nd hole.

Karlsson never looked back after eagling the par-five fourth in the afternoon against an out-of-sorts Cabrera.

Quarter-final results: