Australia captain Steve Smith "crossed the line" by breaking rules on getting help from his dressing room with the decision review system, India skipper Virat Kohli says.

Smith, 27, was caught looking up to his side's camp as he considered reviewing an LBW decision in Australia's second Test defeat in Bangalore.

"There is a line that you don't cross on a cricket field," said Kohli.

Smith admitted his actions, saying "I shouldn't have done that."

He added: "It was a bit of brain-fade on my behalf. I think it was the first time it's happened."

Smith was immediately waved off the field by umpire Nigel Llong as he looked to the Australia dressing room following a chat with non-striker Peter Handscomb, having been given out LBW for 28 to Umesh Yadav.

However, Kohli, 28, alleges he saw Australian players looking to the dressing room for DRS assistance on two other occasions while he was batting.

"When [Smith] turned back, the umpire knew what was going on exactly," he added.

"I pointed that out to the umpire as well that I had seen their players looking upstairs for confirmation.

"We observed that, we told the match referee and the umpire that it's been happening for the last three days and it has to stop.

"Sledging and playing on the opponents' mind is different. I don't want to mention the word, but it falls in that bracket. I would never do something like that on the cricket field."

Asked by an Australian reporter if "the word" was cheating, Kohli replied: "I am not saying that, you did."

Smith's actions were also condemned by former India batsmen Sunil Gavaskar and VVS Laxman.

"It was quite blatant and Peter Handscomb suggested to Smith and then Smith asked the guy at the dressing room," said Gavaskar.

"I don't think that was in the spirit of the game. We have to see what the ICC and match referee do."

Laxman tweeted: "Really disappointed with the way Steve Smith looked at the dressing room to take a review. Totally against the spirit of the game?"