Rory McIlroy’s bid for a record-equalling eighth Race to Dubai title suffered an opening-day setback when a two-shot penalty left him eight strokes behind Abu Dhabi Championship leader Francesco Laporta.

The six-time major champion was penalised for improving his lie by pressing down grass behind his ball with his club before a chip at the par-four 12th at Yas Links.

The DP World Tour confirmed in a statement that McIlroy had breached rule 8.1b(4), which permits a player "to ground their club lightly right in front of or behind the ball".

The statement added: "Ground the club lightly' means allowing the weight of the club to be supported by the grass on or above the ground surface and there is no penalty even if the lie is improved.

"However, a player is not allowed to press the club on the ground."

Applied after his round, the penalty turned a six at the 12th into a quadruple-bogey eight — his only dropped shots of the day — and changed his score from a four-under 68 to a two-under 70.

What had looked a promising start for the Northern Irishman instead left him with ground to make up after Laporta set the pace with a sparkling 62.

McIlroy, 37, accepted the ruling, saying that while "obviously there's no intent" on his part, he was "happy" to take the penalty.

"I play by the rules," said the world number two.

He added: "I try to do everything that I can to never end up in these positions.

"But just by looking at the video, like it doesn't look very good. Obviously that wasn't my intent. I'm just trying to get a feel for the lie."

The incident followed his first chip at the hole, his third shot, which rolled back down a hill into a divot. A tuft of grass appeared to move when he pressed his club down behind the ball before his next attempt.

"The ball is in a sort of bottom of a sandy divot," he added.

"I'm trying to feel like if I can get a 54-degree [wedge] on to the back of the ball, but in the process, this piece of grass has sort of laid down, and I guess the technical term for the rule is if you press down on the piece.

"I don't feel like I pressed down. But at the same time, I don't want the perception of people thinking like I got away with something either, so I'm happy to take a two-shot penalty and move on and move into tomorrow."

The revised score put McIlroy alongside Race to Dubai leader Eugenio Chacarra on two under.

American Patrick Reed, second in the season-long standings and one place ahead of McIlroy, opened with a 74.

McIlroy had reached the turn in a two-under 34 and added a birdie at the 11th before his round unravelled at the next hole, where his opening chip from just off the green rolled back to his feet.

He responded with three successive birdies from the 14th, but could not pick up another shot at the par-five last before being informed of the rules incident.

Chacarra, who leads playing partners Reed and McIlroy in the Race to Dubai after three victories this year, mixed six birdies with four bogeys. Reed’s round ended with a double bogey after he found water at the final hole.

While the marquee three-ball struggled, Laporta seized a three-shot lead with his opening 62.