Australian quick Josh Hazlewood has called for the removal of the 'soft signal' rule from cricket.

The rule - and the use of technology to assess the validity of catches low to the ground - flared up for the second time during the third Test between Australia and South Aafrica during Day 4.

After a controversial decision to overrule an on-field soft signal of out during Australia's first innings when Marnus Labuschagne edged a ball in the direction of South African spinner Simon Harmer, Steve Smith was denied a stunning catch during South Africa's innings.

Dean Elgar edged a ball off Hazlewood towards Smith at second slip, with the former Australian captain diving low to his right.

An on-field soft signal of not out was on this occasion agreed with by third umpire Richard Kettleborough.

Hazlewood, speaking after play, said the soft signal needed to be taken out of the game to remove the guess work.

“I think you should probably take the soft call completely out of it,” said Hazlewood.

“Obviously the two umpires aren't sure on the field and I guess they should just go straight to the third umpire when they're uncertain - you make the call.

“They're sort of biased by that decision on-field and can't find a lot to overturn it.”

While the soft signal process no longer needs conclusive evidence to overturn an on-field decision, it still has the ability to sway a third umpire.

Former ICC umpire of the year Simon Taufel said on Channel 7s coverage of the Test however that he believed the decision for Smith's catch to be denied was the correct one, despite Hazlewood saying he thought both catches so far in the Test that have been reviewed were out.

“When the fielder first touches the ball, they have to have complete control over the ball and their movement, and the ball can not touch the ground,” Taufel said.

“I'm very happy Richard (Kettleborough) has made that call.”