"Is this shirt offensive?"

*Warning: PIRATE RADIO presentation*

The display of a t-shirt that features a semi-naked nun and makes an obscene reference to Jesus has sparked a threat to call police and pleas for a boycott.

For an exhibition starting tomorrow, Canterbury Museum planned to display items including English metal band Cradle of Filth's "Vestal Masturbation" t-shirts.

The clothing, the subject of several controversies and prosecutions worldwide over the years, featured an obscene slogan about Jesus on one side and a picture of a semi-naked nun masturbating on the other.

Conservative lobby group Family First called the exhibit "horrific" and "offensive" and was appealing to authorities, the public and the museum to take action.

Bob McCoskrie, the group's national director, said he was complaining to police because he needed to "warn families" and dismissed suggestions his complaint would simply give the exhibit more attention.

"It's a free exhibition in a public museum."

Mr McCoskrie understood the museum received an "exemption" to display the t-shirts, even though he said both the Internal Affairs Department and Invercargill District Court had in the past deemed the shirt offensive.

"We don't think it's art."

He wanted the t-shirts removed and would encourage people to boycott the museum if it didn't show a "moral conscience" and take the display down.

" We don't think any group should be subjected to this level of vile hate language," he added.

Canterbury Museum director Anthony Wright told NewstalkZB the exhibit's purpose was to tell the story of T-shirts within street art culture, without unduly censoring the content.

"We've got to balance that up against anyone that might be offended, and we've bent over backwards to make sure that anyone who might be offended won't come into contact with anything offensive. It's a tiny part of the overall exhibition," Mr Wright said.

The museum has not immediately responded to a message seeking further comment.

Meanwhile, a Cantabrian anti-abortion campaigner has started an online petition calling for the t-shirt's removal.

The Change.org petition has today attracted over 3000 supporters.

Three years ago, an Invercargill retailer was ordered to destroy his stock of Vestal Masturbation garments and was charged with possessing objectionable material.

In 2008, the Chief Censor banned the same t-shirts, making it illegal to wear, sell, or distribute the garments.

In 1998, the national museum, Te Papa, drew the wrath of some Christians who objected to its display of the "Virgin in a Condom" statue. Former MP John Banks tried prosecuting Te Papa, but the Solicitor General said a prosecution should not proceed due to freedom-of-expression provisions in the Bill of Rights Act.

The "T-Shirts unfolding" exhibition runs from tomorrow until Sunday, May 10.