The 34-year-old was pictured on a skiing trip in Verbier, dancing and drinking, while his family remained in London.
The Duke of Cambridge missed Monday’s Commonwealth Day festivities, including a service in which the Commonwealth Games baton set off from Buckingham Palace, in an event considered one of the most significant in the royal calendar.
The Queen, Prince Philip, Prince Harry and Prince Charles were all present.
Speaking on Good Morning Britain, Morgan said: “I agree with the front pages criticising him.
“There was a huge Commonwealth event in this country, every other member of the royal family turned up – and the next in line to the throne is out gallivanting on the ski slopes, chatting to blondes and dancing like a raver!”
“I have a lot of respect for them. But he is second in line after Charles to be king.”
Royal supporters instantly took the presenter to task on Twitter, with @Katycakes firing back: “Leave him alone Piers Morgan you absolute twat.”
Lynette Hartley tweeted: “Let the guy have some fun. It’s great to see him letting his hair down. #princewilliam rocks.”
@HappySarah echoed the sentiment: “Prince William is allowed to laugh and dance like the rest of us. I want to see him being normal.”
According to analysis by the Press Association, Prince William has spent 13 days this year carrying out royal duties.
His wife Kate has performed 12 days, Harry 17 and the Queen, who will turn 91 next month, has completed 24.
Graham Smith, chief executive of anti-monarchy campaigners Republic, told Sky News: “The taxpayer has stumped up millions of pounds to give him a palatial London home and provide round-the-clock security – expecting him to do something for the country in return.
“If he’s not interested in fulfilling his side of the bargain we should kick him out of Kensington Palace and insist he pays his own way.”
Morgan later tweeted: “I don’t care about Prince William going on the lash with his mates. I do care he missed a huge Commonwealth Day event to do it.”
Last year the Prince was criticised as “workshy”, but countered with the insistence: “I take duty very seriously. I take my responsibilities very seriously. But it’s about finding your own way at the right time and if you’re not careful, duty can wear you down at a very early age.
“I think you have got to develop into the duty role.”
Prince William has endured an uneasy relationship with the media, and has previously come in for scorn by Morgan.
Last year Morgan accused the father-of-two of “sloping off” from his duty as a senior royal, by travelling to a French ski resort with his wife and children and only sanctioning pictures taken by an official photographer invited on their trip.
Writing for the MailOnline, Morgan grumbled: “They get to live in massive palaces, fly in private jets, be chauffeured around in the world’ best cars and get waited on hand and foot by a flotilla of liveried servants.
“In return, they agree to be on public parade for endless rounds of often incredibly tedious events. And they agree to play the game with the media.
“So what’s the problem, I hear you cry? Well, it’s this: Prince William hates the press and this is a very deliberate and unacceptable attempt to shackle and control them.”