The behaviour of pop star Robbie Williams during the summer's concert at Slane Castle has led to criticism from a British television watchdog of Sky One, which screened the event live.
During the performance, Williams used the f---- word just after the 9 p.m watershed, made an obscene gesture and joked he would expose himself.
The Independent Television Commission in Britain has ruled that his antics, and "Sky's failure to respond to these problems", breached programme guidelines.
The ITC's programme code warns broadcasters to be sensitive to a family audience if a show begins before 9 p.m., as the Williams concert did.
Sky said the singer - voted the sexiest man in the world last week by readers of a women's magazine - had been briefed that swearing was unacceptable and it wished to apologise to anyone offended. It felt the sexual gesture was unclear and would not be understood by children.
Sky said there had been no problems in rehearsals but it would be more careful about briefings in future.
The ITC was concerned that Sky did not have a back-up strategy to respond to such situations. An ITC spokeswoman said: "There's always going to be potential difficulty with live events and we would expect some measures to be put in place in advance."