Najam Sethi, the chairman of the interim management committee running the PCB, has said the Pakistan board wants clarification from the ICC on the "inconsistency" in the application of the ball-tampering rule. Pakistan's Shahid Afridi was banned for two Twenty20s in early 2010 for a ball-tampering offence that was loosely similar to the one involving Faf du Plessis in Dubai, for which du Plessis has been fined.

Sethi tweeted on Saturday evening: "PCB is writing letter to ICC seeking explanation of inconsistency by match referee in application of ball tampering rule to Afridi vs Faf." The PCB confirmed to ESPNcricinfo that this was the case.

Waqar Younis, speaking to ESPNcricinfo after the Test finished, also believed the fine was lenient: "I think, to be very honest, Faf got away with it with just 50% of the match fee. I thought it was a bit of frustration from the South Africans, they did not need to do that. It leaves a big question mark on South Africa's credibility."

Ball-tampering, which is a level two offence, comes with a fine of 50 to 100% of the match fee, and/or a ban of one Test or two limited-overs games.

A screen grab of Shahid Afridi biting the ball

Afridi had pleaded guilty to ball-tampering during an Australia-Pakistan ODI, in which he was captaining, in Perth, In January 2010. He was charged with an article 2.2.9 offence of the ICC code of conduct which relates to "changing the condition of the ball in breach of law 42.3 of the laws of cricket". Afridi was seen on television apparently biting the ball on a couple of occasions. His transgression was picked up the by the third umpire, and reported to the on-field umpires, who, after a chat with Afridi, changed the ball. Afridi was called into a hearing with the match referee Ranjan Madugalle immediately after the match, where he apologised for his actions.

Du Plessis pleaded guilty to the charge of ball-tampering during the Dubai Test on Friday, and was fined 50% of his match fee by match referee David Boon. In du Plessis' case, the incident occurred following television visuals of du Plessis rubbing the ball near the zipper of his trouser pocket. The TV umpire brought it to the attention of the on-field umpires Ian Gould and Rod Tucker, who called Graeme Smith over for a chat and subsequently changed the ball and awarded a five-run penalty against South Africa, sanctions that are consistent with the penalty for unlawfully changing the condition of the ball.

Pakistan captain Misbah-ul-Haq, speaking after the Test, refrained from commenting on the issue. "It has nothing to do with us," Misbah said. "It's between the match officials and their team. It's none of our business."