Clifford boasted about his showbusiness contacts and pretended to be Hollywood figures on the phone in order to reel in his victims, prosecutors alleged.
The 70-year-old denies 11 counts of indecent assault relating to seven alleged victims aged from 14 to 19 between 1966 and 1984.
The public relations guru has become a well-known figure himself through his work to protect and promote the image of celebrities in Britain's tabloid press.
She said Clifford was "wealthy, he is well-connected," and had influence as "the breaker of reputations".
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As a top media player for years, "he knows the strings to pull. He knows how to manipulate, lie and get what he wants," Cottage said.
"As the years went by, he got away with his behaviour. He must have thought he was untouchable and no doubt thought no one would complain and, if they did, they would not be believed."
"The defendant used his contact with famous people to bully and manipulate these young people into sexual acts with him," the prosecutor said.
Cottage said the claims from Clifford's alleged victims emerged following revelations in 2012 that the late BBC presenter Jimmy Savile had been a serial sex offender.
She said their separate complaints were "compelling and detailed and have significant elements of similarity".
Clifford was arrested in December 2012 and charged in April 2013.