Real Madrid have hit back at claims from Barcelona president Joan Laporta that they were "historically favoured" by Spanish referees, publishing a video highlighting Barca's links to the former government of dictator Francisco Franco.

Laporta made the allegation on Monday during an impassioned defence of Barcelona's conduct in making payments totalling €7 million over 17 years to the former vice president of Spain's refereeing committee.

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A court is now investigating the payments -- made to Jose Maria Enriquez Negreira's company between 2001 and 2018 -- and Madrid have formally asked to participate in the case.

"We all know [Real Madrid] have been favoured by refereeing decisions, historically and in the present day," Laporta said during a two-hour news conference on Monday. "It's a club that has been considered the team of the [Franco] regime."

"It's worth remembering that, for seven decades, most of the presidents of the refereeing committee have been ex-members, ex-players or ex-directors of Real Madrid. For 70 years, the people who chose who dispensed justice on the field of play have been people connected to Real Madrid. For them to claim they feel wronged is an unprecedented exercise in cynicism."

Madrid responded with a video published on social media later on Monday, asking "which was the team of the regime?"

The four-minute video details a series of events involving Barcelona during the Franco dictatorship -- which lasted from 1939 until his death in 1975 -- including the inauguration of their Camp Nou stadium by a government minister, and the club honouring Franco with medals.

Madrid and Barcelona have worked together closely in recent years in support of a proposed breakaway European Super League, but that relationship has been damaged by the Negreira case.

Prosecutors say that Barca sought to gain favourable treatment with the payments, while Laporta insisted on Monday that the club have been victims of a "smear campaign" and Negreira's services -- performed by his son -- were limited to scouting and technical refereeing reports.

Madrid announced last month that they would take part in the proceedings, saying it was "deeply concerned about the severity" of the allegations.