Nick Kyrgios refused to apologize for his Miami Open meltdown Tuesday and insisted he couldn't care less about receiving further sanctions from tennis bosses.

Kyrgios, who was fined $25,000 for racquet abuse and verbal obscenities after losing to Rafael Nadal in Indian Wells earlier this month, lost his head in the Miami heat and spent his fourth-round match delivering a blistering verbal assault on "dreadful" Brazilian match umpire Carlos Bernardes before crashing out 7-6 (7/3), 6-3 to Italy's Jannik Sinner.

The Australian became involved in a running war of words after the walkie-talkie of Bernardes went off mid-point in the first set.

Kyrgios was seething with Bernardes, who was also in charge of his controversial match with Nadal, calling him "an absolute clown" before raging: "This is one of the biggest tournaments and you guys can't do your job. It's embarrassing."

The Aussie also snapped: "You wonder why no one watches this sport. It's a laughing stock."

Kyrgios refused to let his anger lie and, having already received a code violation for an audible obscenity, was hit with a point penalty at 5-3 in the first set tie-break for unsportsmanlike conduct after appearing to talk with a friend who was sitting courtside.

A game penalty was then issued at the start of the second set after Kyrgios shattered his racquet.

"I just don't think he (Bernardes) controls the crowd well at all," the Australian told AFP.

"For the point penalty, all I said to my team was that Matthew Reid, an ex-player, could do just as good a job. If that's worth a point penalty at a Masters event, that is ridiculous in my opinion.

"When everyone in the crowd is booing an umpire and he is becoming the center of attention, that is not his job. No one in the stadium came to see him talk or do what he does.

"You've got Jannik Sinner who is one of our greatest stars and, not to toot my horn, the majority of people are there to watch me play.

"And you have a guy talking while I was 40-0 up. He was talking. I was like 'what are you doing?' The crowd actually hated him that much they told him to be quiet. If you are getting booed by the crowd you are not doing a good job.”