Locals angry after lauded artwork disappeared from public view and re-emerged on US website with £450,000 guide price

A Banksy mural has been put up for auction on a US website with a guide price of up to £450,000 after being removed from a building in north London.

The artwork of a barefoot boy using a sewing machine to stitch union flag bunting, apparently in a sweatshop, appeared on the outside wall of a Poundland shop in Wood Green in May. It was widely interpreted as condemning child labour and mocking the impending Queen's diamond jubilee celebrations.

Haringey councillor Alan Strickland said locals were angry at the removal of the mural and urged people to email the auctioneers to demand that it be removed from sale.

It was discovered to have been removed over the weekend and later emerged for sale with Fine Art Auctions Miami with a guide price of $500,000 to $700,000 (£323,000 to £452,000). Bidding for the picture, titled "Banksy Slave Labor (Bunting Boy). London 2012", closes on Saturday.

A Poundland spokeswoman said the company was not the owner of the building and had not removed the artwork. The store tweeted: "We would like to confirm that we are not responsible for either selling or removing the Banksy mural. We are currently investigating."

The owner of Fine Art Auctions Miami, Frederic Thut, told the Sun it was being offered for sale by a well-known collector who he refused to name. He added: "The collector signed a contract saying everything was above board."

The picture is popular with locals and had attracted tourists to the area, with signs put up at the local tube station directing visitors to the mural. It had also been covered with acrylic to protect it.

A local resident told Haringay Online the artwork had been surrounded by scaffolding and tarpaulin since last Wednesday. She said she discovered it had been removed on Sunday when she checked under the tarpaulin.

In the past, Banksy has declined to authenticate works attributed to him that were up for auction because of a belief that street work should remain in its original location.

• This article was amended on Monday 18 February to correct the spelling of Haringay Online.