Police hurried to the scene when a passer-by complained about a nude painting in a charity shop window.
Volunteers at the Sussex Beacon store at George Street, Hove, said officers told them to conceal prominent parts of the naked man.
But helpers thought the police had their priorities wrong.
Assistant George Fulton, 34, said: "The painting was not pornographic - you see more on Page Three of The Sun. There was nothing offensive about it but somebody complained to the police.
"The shop manager got a phone call from the police and as soon as he had put the phone down two officers were already there. It was as if there had been a murder.
"The constables asked the manager to cover up the private parts. If I had been there I'd have said no, it's a work of art.
"But we put a vase in front of it. It was eventually sold for £29.99 but it should have made £99 and that, I believe, was because it couldn't be seen.
"If we can't display things in the front window, how are we supposed to sell them?"
Mr Fulton said the shop's varied stock made it a particular target for shoplifters, who have stolen CDs and videos recently.
He said: "The shop is like an Aladdin's cave. But these people are not stealing from us, they are stealing from the sick and dying in the hospice."
No one from the police was available for comment.
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