Banksy's insistence on keeping his identity a secret has cost the Labour party £75,000 ($136,600), the Independent reports.

The star street artist donated one of his canvases, Sketch for Essex Road, to an auction at Aquarium Gallery last March meant to raise money for Ken Livingstone's mayoral re-election campaign. When bidding for the work, which depicts two children pledging allegiance to a Tesco bag on a flagpole, reached £195,000, Labour leaders were thrilled. It was only after the fact that they realized that they could not accept the full amount because of electoral funding laws.

The rules ban anonymous donations of more than £200. If the party had accepted the full £195,000 paid for the work, then the Banksy donation would have to have been declared a gift and his true identity released on the Internet.

Instead, Labour worked out a plan with the Electoral Commission to negate Banksy's gift by setting the market value of the painting at £75,000 and returning that amount to the gallery. Steve Lazarides, the winning bidder, in turn gave a "separate" donation of £121,600 to the party. In this scenario, Bansky technically donated his work for free and could therefore retain his anonymity.

A Labour spokesman said the party was "satisfied that all our donations fully comply with the law." Another party source commented: "This has certainly been more complicated than running a raffle."