The American artist bought the Banksy piece at Julien's auction house on November 14 for $730,000 (£561,000) and vowed to whitewash the work as a mark of protest against street art being bought and sold.
"My idea for this painting is to whitewash it for my good pal Banksy, I only wish I could've spent more money for it," English said.
"I'm going to paint it white again, I'm done. This is a blow for street art. It shouldn't be bought and sold. I'm going to paint over it and just include it in one of the walls in my house. We're tired of people stealing our stuff off the streets and re-selling it so I'm just going to buy everything I can get my hands on and whitewash it."
The artist, however, hopes to sell the whitewashed art for a mint of money, according to The Independent.
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The anonymous Banksy character gave an opinion on the kerfuffle on its official website.
Banksy was asked: "what do you think about the auction houses selling street art?" The artist replied with a Henri Matisse quote: "I was very embarrassed when my canvases began to fetch high prices, I saw myself condemned to a future of painting nothing but masterpieces."
Banksy commented on the subject through its publicist: "For the sake of keeping all street art where it belongs I'd encourage people not to buy anything by anybody unless it was created for sale in the first place."
Banksy's "Slave Labour" mural was painted on the wall in Wood Green, north London. It shows a young boy, whose attention is focused on a sewing machine, on his knees making Union Jack bunting. The art is believed to be a thinly-veiled protest against mass-produced London Olympics 2012 souvenirs, calling for an end to exploitation in the name of capitalism.