The singer - who received damages of £600,000 from News Group newspapers after her phone was hacked when she was 16-years-old - told the BBC Wales News website that she believed the newspaper's decision to publish the pictures was a step too far.
"The pictures were available on the net if you wanted to see them and if you wanted to form your own opinion," she said.
"I don't think they [The Sun] needed to go that step further to print them. It was in a private hotel room. I think it was an invasion of his privacy.
"I'm not a royalist, I don't sit on either side of the fence."
The Sun printed two photos of the prince and a naked woman taken in a Las Vegas hotel room last week. The press watchdog has since received more than 850 complaints but the newspaper says they were testing press freedom and that its readers had a right to see them.
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