Australia sealed a series win over New Zealand to reach the top Test ranking on Wednesday but captain Steve Smith was forced to defend their aggressive style as he was fined over a row with the umpires.

With Smith smacking 53 off 46 balls, Australia polished off the 131 runs they needed on the last day.

The match had no sooner finished than Smith was charged over Tuesday’s profanity-laced confrontation over an lbw decision that had already seen fast bowler Josh Hazlewood fined 15 percent of his match fee.

The ICC later said Smith was fined 30 per cent of his match fee after he admitted showing dissent by questioning the decision that Kane Williamson was not out.

Wednesday’s win confirmed Australia’s superiority after they won the first Test by an innings and 52 runs, and allowed them to overtake India as the world’s top Test side.

“It’s always special when you get to number one in the world. That’s our goal as a team to be number one in the world in every format of the game,” Smith said.

However Smith also had to dispute suggestions that Australia, often controversial over their uncompromising play and habit of sledging the opposition, were cricket’s bully boys.

“I don’t think we’re not nice guys. We play a good hard, aggressive brand of cricket,” he said. “For us it’s about knowing where that line is and myself and Josh Hazlewood have crossed that line in this Test match and that’s not what we’re about. Hopefully, we can learn from that and continue to develop as a team and get better.”

Smith said he believed at the time he was acting correctly to question the umpire’s call.

“I thought I was well within my rights to go up to the umpire and ask him why we didn’t use the real time snicko,” he said referring to the technology used to determine if the ball had hit the bat.

“That’s deemed to be dissent and I’ll cop that on the chin and I need to be better as a leader, I need to set the example and that was not good enough.

“For me, it’s about trying to learn from my mistakes and improve and try and get this team going forward in the right direction and playing the good aggressive brand of cricket that we play so well and know there’s a line there that we can’t cross.”