South Africa's Branden Grace insisted his conscience was clear after receiving a controversial drop in the first round of the BMW PGA Championship.

After making an eagle on the 12th to move into a tie for the lead at Wentworth, Grace's approach to the 13th plugged in the bank of a bunker, leaving him with an awkward lie on the upslope.

However, after taking his stance in the sand, the 29-year-old called in a rules official and said that his feet were touching the rubber sheeting at the base of the bunker, thereby entitling him to a free drop.

The decision was met with criticism on social media, with former Masters champion Danny Willett writing on Twitter: "@EuropeanTour please explain that drop?! Burying feet enough in to get to the base of the bunker???"

Former Ryder Cup captain Paul McGinley labelled the ruling "ridiculous" before adding: "If you twist your feet enough you're bound to eventually reach the bunker lining.

"That means any time a player wants relief from a poor lie he can simply twist his feet until he reaches the bunker lining. That can't be right."

Grace, who bogeyed the 13th and dropped another shot on the 16th in an opening 68, said he had simply applied the rules after experiencing a similar situation.

"I actually knew the ruling from a couple of years ago in China at the HSBC Champions," he said.

"My ball was found outside the bunker, but the only stance I had was inside the bunker and the same thing happened.

"When I took the stance, there was only one or two inches of sand and my foot kept sliding on the material, the rubber, underneath the sand.

"A rule is a rule, and I took advantage of the rule there, and it helped knowing the rule in some respects. Fortunately for me, I got away with a good drop but I still made bogey.

"I can understand if some people criticise you for standing in the middle of the bunker and going too deep, but if you're standing on the upslope it's not always easy getting a stance.

"It's quite a steep upslope there. I was trying to get a stance with my right foot, but my left one I didn't have to do too much. The right one was sliding down most of the time and then obviously getting down into the sand I was touching the rubber.

"A rule's a rule, and that's exactly what the rules official is there for."