Max Clifford has been told he must serve at least half the eight-year sentence handed down at Southwark Crown Court in prison.
Judge Anthony Leonard told Clifford he had shown a "contemptuous attitude" and "quite extraordinary behaviour" while showing "no remorse" for his crimes.
The judge said: "These offences may have taken place a long time ago, when inappropriate and trivial sexual behaviour was more likely to be tolerated, but your offending was not trivial, but of a very serious nature."
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"My sincerest apologies to everyone who purchased tickets and were planning to come to the upcoming shows."
His comments at the Defence and Security Forum on Monday came after a £20 billion black hole in the budget for the next decade emerged.
The Foreign Secretary said he thinks the health service should be "at the very top of the list" for a windfall after the UK leaves the EU.