James Anderson and Joe Root inspect the ball, Dec 29, 2017/Getty Images

England's treatment of the new ball came under the spotlight on the fourth day of the fourth Ashes Test at the Melbourne Cricket Ground on Friday, when the umpires had a tense discussion with captain Joe Root about their bounce returns.

Umpires S Ravi and Kumar Dharmasena spoke to Root after Stuart Broad threw the ball from mid-on that bounced well short of wicketkeeper Jonny Bairstow on the hard wicket block. Bounce return is a tactic used to scuff one side of the ball and quickly attain reverse-swing.

Questions were also raised over TV footage of James Anderson paying close attention to the quarter-seam that runs down the face of the ball.

"I'm not sure you are allowed to use your fingernail there," Shane Warne said on Nine's Wide World of Sports broadcast.

"If you are going to touch the ball at all, it's not just shining it, you want to do it right in front of the umpire so they know there is nothing untoward going on. But I'm not sure that Jimmy Anderson ... this might get some people talking."

"Ball reversing under 10 overs," former pacer Mitchell Johnson tweeted during today?s morning session.

Former Australia batsman Michael Hussey said Anderson could face censure for the episode.

"It didn't look great, to be honest. There might be a little bit of a 'please explain' there for Jimmy Anderson? The pitch is pretty flat and they've got to look at other ways to put the batsmen under pressure and reverse swing is one of the weapons they can use.?

Alyssa Healy, Australia women's team wicketkeeper and wife of injured fast bowler Mitchell Starc, suggested the match referee may take an interest.

Rain hampered England´s bid for victory on the fourth day of the MCG Test, with David Warner and Steve Smith also offering resistance at the crease.

At tea after two rain delays, Australia were 103 for two and trailing the tourists by 61 runs after England´s first innings ended on the first ball of the day.