The picture appeared on the wall of a Poundland store on Whymark Avenue in Wood Green, north London.
A professor specialising in Bansky believes it is the Bristol-born artist's work.
A Poundland spokesman said the retailer enjoyed Banksy's art and said suppliers met ethical guidelines.
Curious passers-by have been scrutinising the stencilled image, which was adorned with real bunting.
One man travelled from Heathrow Airport having just arrived in the UK from Spain.
Jason Cobham, 44, from Wood Green, said: "I definitely think it's a Banksy. It keeps you thinking about the plight of child labourers."
He added: "I'd pay more than a pound for it. If I could get it off the wall I'd pay a lot of money for it. Haringey should celebrate it."
Ernesta Zazdokaite, 19, from Haringey, said: "It's nice but what's it all about?"
Professor Paul Gough, from University of the West of England, an academic who studies the artist, suggests the image has all the hallmarks of a genuine Banksy.
He said: "The stencil is very well cut, the quality of the spraying and that unique feathered edge that he is able to achieve when painting white on to black is reminiscent of several other pieces in the capital.
"The bunting is a brilliant touch, short-lived but with lasting impact in the memory given this royal anniversary year."
Tim McDonnell, retail director of Poundland, said: "We are fans of Banksy and we are proud supporters of the Queen's Jubilee.
"Poundland has a clear defined code of conduct for all our suppliers and a strong ethical stance on all labour issues."
A spokeswoman for Haringey Council said she believed the wall was private property and the council had no right to remove the painting.
She said in cases where graffiti is found to be offensive, the council can help the property owner remove it.
She added: "This is different. They may well like this."
The last image in Haringey believed to have been painted by Banksy appeared in September 2009 in Tottenham High Road.
It showed children playing with a No Ball Games sign and has since been covered with Perspex.
Graffiti artist Banksy is believed to be behind a new painting which shows a boy hunched over a sewing machine stitching union flag bunting.