A mural by famed street artist Banksy is up for sale at a Miami auction house after the work, and a chunk of the North London wall it was spray-painted on, vanished late last week.

The elusive artist’s trademark spray-paint stencils offering ironic social commentary are never verified, but they are hotly sought after by collectors

Who owns the mural is unclear, and how it ended up in a Miami auction house shortly after going missing is still a mystery.

Frederic Thut, owner of Fine Art Auctions Miami, which is selling the piece, said his firm has done “all necessary due diligence” to establish the ownership of the work.

“Unfortunately we’re not able to provide any information by law and contract about the details of this consignment,” he said.

The mural was painted on a building occupied by Poundland Stores, a British retailer that sells various items for only a pound. The work, titled Slave Labour, shows a young boy kneeling at a sewing machine with Union Jack bunting.

It appeared in 2012 during Queen Elizabeth II’s Diamond Jubilee, celebrating her 60th year on the throne. The Poundland chain was a focal point of controversy in 2010 when it was alleged that it sold goods made by Indian children as young as seven.

“We leased the premises from a landlord and were as shocked and surprised as anyone at the removal of the Banksy artwork,” Kate Gibson, a spokeswoman for Poundland, wrote in an e-mail. “We understand the upset this has caused and in no way do we condone the removal of the artwork without proper consultation with the community.”

Meanwhile, the work remains listed on the auction house’s website, where it has received three bids and is valued between $500,000 (€373,000) and $700,000 (€522,000). Described as a “unique street work” of “stencil and spray paint on render with additional jubilee bunting,” it is due to be auctioned on Saturday.

The elusive artist’s trademark spray-paint stencils offering ironic social commentary are never verified, but they are hotly sought after by collectors.

One West Bank mural shows a young girl frisking a soldier who looks to be leaning up against a wall with his arms outstretched. Another is of a man with a bandana wrapped around his face looking as though he’s throwing a grenade, though a bouquet of flowers takes the place of the explosive.

“Banksy goes to a property anywhere around the world and he puts something without asking you on your wall,” said Stephan Keszler, a New York City gallery owner who specialises in Banksy’s work. “People call it vandalism, therefore he’s not authenticating the works because this would admit that he made a crime.”

Keszler brought more than a half dozen Banksy murals – massive concrete slabs weighing more than 907kg – to a Miami art fair in December. Two were works he salvaged on behalf of building owners in the West Bank and later bought.

A group called Pest Control oversees authentication of the artist’s works on paper, but the group is almost as elusive as Banksy himself. Keszler said Holly Cushing, a producer of the 2010 documentary about the artist, Exit Through the Gift Shop, runs the group.

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