KitKat copycats could be on the prowl after the top lawyer at the European Court of Justice decided not to give Nestle a break over its attempts to trademark the plain four-fingered bar.

The case dates back to 2010 when KitKat owner Nestle sought to register the shape of the four-bar treat without the brand's logo.

Cadbury contested this in 2011, and was backed by a UK court in 2013. which found the trademark was “devoid of inherent distinctive character”. Nestle subsquently appealed this decision.

Today the ECJ's advocate general Melchior Wathelet said it was “not sufficient” for Nestle to prove that consumers recognise the shape of the bar as being that of a KitKat.

“[Nestle] must prove that only the trade mark in respect of which registration is sought, as opposed to any other trade marks which may also be present, indicates, without any possibility of confusion, the exclusive origin of the goods or services at issue.”

Iain Connor, intellectual property lawyer at Pinsent Masons, said: “It seems that like the old ‘elephant test’ [ie ' it's hard to describe but instantly recognisable when spotted] isn’t enough for trademark lawyers.

“Despite the fact that consumers know a KitKat when they see one, the advocate general has said that the Court needs to see evidence of a level of acquired distinctiveness way beyond “mere recognition”.

“The opinion is entirely consistent with the Court’s previous refusal to grant trade mark protection for Lego bricks and so comes as no surprise.”