The Hollywood actor Sylvester Stallone today admitted that he illegally imported banned body building drugs into Australia.

The Rocky and Rambo star is known as much for his muscular physique as his acting skills. He pleaded guilty in a Sydney court to bringing 52 vials of a banned human growth hormone and testosterone into the country.

The 60-year-old actor was not in court himself, but his lawyer handed a letter from Stallone to the judge. “I made a terrible mistake. Not because I was attempting to deceive anyone but I was simply ignorant of your official rules,” he wrote. “I wish to express my deepest remorse and again apologise for my actions.”

Stallone was in Australia to promote Rocky Balboa, the sixth instalment of the boxing franchise, which the “Italian Stallion” wrote, directed, produced and starred in.

He was detained at Australian customs on February 16 with vials of the human growth hormone Jintropin. Stallone’s lawyer Philip Boulten told Sydney’s Downing Centre Local Court that his client had a US prescription for the drug, although the prosecution insisted that it was also banned in America.

Jintropin is designed to reduce wrinkles, increase muscle mass, reduce body fat and increase sex drive.

Mr Boulten told the court Stallone’s use of the drug was on the advice of his doctor and due to an unspecified medical condition. “This is not some back-alley body builder dealing covertly with some banned substance in some sort of secret way,” he said.

“His apology to the court is an apology in broad terms, meant to convey both to the general public, the community, and to the justice system itself, his regret at having been involved in his possession of the substances in contravention of Australian laws.”

Prosecutor John Agius said the court should give the strongest possible sentence as a deterrent. “That message is just as important for a celebrity like Sylvester Stallone as for the average Australian citizen,” he said.

He dismissed the claim that Stallone was unaware that he was breaking the law. He claimed the actor threw four vials of testosterone from his hotel window when customs officials carried out a raid on his room three days after he entered the country.

The maximum fine for the offence is A$110,000 (£46,287) but Stallone faces a top penalty of less than £10,000 as the case is being heard at a local court.

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