Liam Lloyd Warriner, a barman, was fined Tuesday by a Brisbane court a sum of 500 pounds for creating public nuisance.
He said his act was a political protest to show his contempt for the British monarch during her visit to Queensland in October last year, the Daily Telegraph reported.
The court heard that the man dropped his trousers and ran alongside the queen's motorcade for 50 metres, with an Australian flag clasped between his buttocks.
It was not clear whether the queen observed the act.
"I'm a proud anti-monarchist. What's uncivilised about it? We come into the world naked," Warriner said.
"Any self-important, self-propagating elitist, I will happily bare my buttocks to," he said.
"The queen represents where people can be born into importance. I don't think that any one family should have any more importance than any other family on this planet," he said.
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