Banksy has lost a legal battle with a greeting card company over the trademark of one of his pieces, with a ruling from Europe saying that the artist's anonymity hurt his case.

The EU's intellectual property office said that Banksy's trademark for the piece Flower Thrower was made in bad faith - and rendered it "invalid in its entirety".

Pest Control Office Ltd - which handles requests dealing with the artist's works - had been embroiled in a dispute with card makers Full Colour Black Ltd.

The Flower Thrower piece is also known as Love Is In The Air and shows a masked man about to throw a bunch of flowers. Banksy created the work in Jerusalem in 2005.

Banksy loses trademark for iconic work created in Jerusalem https://t.co/tva3sUgNje pic.twitter.com/x63NpdYf2g

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Full Colour Black sells a range of cards that feature the work of the artist. They claimed a 2014 trademark for Flower Thrower should be cancelled because it had not been used.

They claimed the trademark was only filed to stop "the ongoing use of the work which he had already permitted to be reproduced".

The card company added that Banksy wrote in one of his books that "copyright is for losers".

After the legal case was started, Banksy opened his own online shop called Gross Domestic Product.

But examiners in the cancellation division of the EU's intellectual property office were not swayed by the artist's argument.

They wrote in their decision: "It was only during the course of the present proceedings that Banksy started to sell goods but specifically stated that they were only being sold to overcome non-use for trademark proceedings and not to commercialise the goods."

They added: "It must be pointed out that another factor worthy of consideration is that he cannot be identified as the unquestionable owner of such works as his identity is hidden.

"It further cannot be established without question that the artist holds any copyrights to a graffiti.

"The contested (trademark) was filed in order for Banksy to have legal rights over the sign as he could not rely on copyright rights but that is not a function of a trademark."