The graffiti artist Banksy is offering voters free limited edition prints if they vote against the Conservative party.
A statement on the artist's website asked voters to show they had voted against Conservative candidates by sending pictures of their ballot papers.
The controversial artist also took to social media to convey his message.
The full statement read:
Rules against influencing the votes of other people include giving food, drink, entertainment or provision to make someone vote a certain way.
The Electoral Commission has also warned people against taking pictures of their ballot papers, although there is legal confusion about the issue.
A small 'lawyer's note' appearing under the statement on Banksy's website read:
Banksy's spokeswoman Jo Brooks confirmed the artist had made the offer.