Barcelona president Joan Laporta insisted Tuesday his club have never "bought referees" amid investigations into payments made to a former refereeing chief over several years.

The Catalan side paid a reported 6.5 million euros ($6.9 million) between 2001 and 2018 to a company owned by Jose Maria Enriquez Negreira, a former vice-president of the Technical Committee of Referees (CTA) in Spain, for what they said was advice on refereeing matters.

Spanish prosecutors are investigating the payments and Spanish newspaper El Pais said Tuesday they intend to report Barcelona for "continued sporting corruption".

"Let it be clear Barca have never bought referees and Barca have never had the intention of buying referees, absolutely never," said Laporta at an event in Barcelona.

"The forcefulness of the facts contradicts those who try to change the story. We are doing well again - nothing is chance."

Laporta previously criticised La Liga president Javier Tebas for a "pushing a campaign" against him and hinted at it again.

"There is a campaign to damage Barça's interests," continued Laporta.

"It is a campaign aimed at controlling the club. La Liga does not accept that Barça did not sign the contract with CVC (a collective media rights deal)."

Laporta said he was considering offering coach Xavi Hernandez a contract extension, with the team currently nine points clear at the top of La Liga, on course for their first league title since 2019. Xavi's existing deal expires in June 2024.

"He's a man who doesn't stretch his arm out beyond his sleeve, he doesn't ask for crazy things and he understands the club's (financial) situation, I have considered Xavi's renewal," said Laporta.

The president also said Barcelona were looking at signing more players this summer, after heavy investment last year was afforded by selling off a percentage of future television rights, among other methods.

"Barca will have to sign a full-back, certainly, and a centre-back if there is a good opportunity," added Laporta.

"Surely a striker, yes, but somebody will have to leave. We have a good midfield and we also have a youth academy with players who will make it to the first team.

"Xavi also has to do this, to promote young players. One more striker would fit, but financially we don't have unlimited resources like a 'state-club'. We must be prudent."