The Spanish football giant Barcelona has told fans it has “no connection whatsoever” with the digital coin offered by its new crypto partner, following criticism over the deal.

Clubs often pick up sponsors in unusual areas to bring in extra money – with Arsenal bringing in Persil as its fabric care partner in 2023, and Kellogg’s becoming Manchester City’s breakfast cereal partner that same year.

But far less is known about Zero Knowledge Proof (ZKP), which signed a three-year sponsorship deal in mid-November with Barcelona.

ZKP then announced a cryptocurrency, prompting concerns Barcelona fans could be led to invest in it – leading the club to distance itself from the coin.

“The club has no responsibility for, or involvement in, the issuance or management of this token, nor does it use the associated technology,” the club said in a statement on its website.

Little is known about ZKP, which also announced a similar sponsorship deal with Australian rugby league team Dolphins in early November.

On its website, it says the project has been founded and developed by “a pseudonymous collective” based across “multiple jurisdictions”.

In other words, the firm is not revealing the names or locations of those behind it.

University of Sussex professor Carol Alexander said the Barcelona brand gives enormous visibility to crypto firms like ZKP – but there is “substantial risk for supporters who buy the tokens”.

“Sponsorship creates an aura of credibility, even when the underlying project is opaque,” she told the BBC – saying this meant fans and supporters should be “very cautious”.

“Before buying any crypto asset they should ask who controls it, where the documentation is, and what recourse they have if it fails,” she said.

“With ZKP, none of those answers are clear.”

Details about ZKP are few and far between, with the firm even claiming it has no single headquarter.

But the Financial Times reported an earlier version of the company’s terms listed an office located in Apia, the capital of Samoa.

The ZKP name is also the term used to describe a type of technology designed to enhance the privacy of a blockchain – a digital record of transactions which underpins cryptocurrencies.

Its deal with Barcelona comes as the football club is reportedly facing an uphill struggle to raise revenue and relieve its debt.

“Barcelona’s finances in recent years have been perilous, so the club appears to have adopted a strategy of ‘bank the money first, ask questions later’,” said football finance expert and author Kieran Maguire.

He told the BBC “crypto products seek legitimacy and normalisation from those that speculate on their products”.

To partner with a football club, particularly one as well-known as Barcelona, “helps achieve those ambitions,” he said.

And former Barcelona youth player Xavier Vilajoana, who reportedly is bidding to be its next president, called on the club to clarify how the deal had come about in a post on X.

He also asked the club about ZKP’s relationship with self-proclaimed misogynist Andrew Tate – one of only three X accounts the crypto firm follows on the platform.

The BBC has approached Barcelona for a response.