Banksy has offered to send a free art print of his work to people who can show they voted against the Conservatives in the upcoming UK election.
He risks breaking election law with the offer as it may be considered an illegal bribe that could influence voters in which party they back.
The artist, who is known for politically-charged graffiti, said he was would be releasing a new limited-edition print on the day after the General Election on June 8.
It will be a copy of his famous 'girl with balloon' work but the red heart will instead be coloured as the Union Jack.
The post said that voters in former Conservative seats in and around Banksy's hometown of Bristol could claim a free print if they sent a photo of their ballot showing they had backed other candidates.
"Simply send in a photo of your ballot paper from polling day showing you voted against the Conservative incumbent and this complimentary gift will be mailed to you," it reads.
The post said the offer was open to people registered to vote in the constituencies of Bristol North West, Bristol West, North Somerset, Thornbury, Kingswood and Filton constituencies.
A "lawyer's note" disclaimer adds: "This print is a souvenir piece of campaign material, it is in no way meant to influence the choices of the electorate".
But the elusive artist may yet fall foul of the law.
The Electoral Commission, which oversees elections in the UK, warns that bribery is an electoral offence.
Banksy could additionally break the law if the offer in considered to be "treating" - when anyone tries to influence a voter by offering food, drink, entertainment or other goodies.
There could also be a legal risk to taking a photograph inside a polling station, the Electoral Commission warned.
"The law in this area is complex," a spokesman said. "The commission's advice is against taking any photos inside polling stations."
Any issues of potential bribery would be a matter for the police, he added.