The letter was sent to the groups as the board also launched a consultation campaign with fans, called ‘Agora OM’.

OM’s Twitter account, followed by over 3.5 million, has been losing about 1,000 followers per hour since the supporters published their statement.

Should the convention be cancelled, the club would be free to sell season tickets at any price they see fit, potentially driving fans away from the Stade Velodrome.

Members of supporters’ groups accounted for around three quarters of the 33,000 season ticket holders last season.

Up until 2015, the supporters’ associations would receive a percentage of the season tickets according to a system set up by Bernard Tapie, the club’s president from 1986 to 1994.

Tensions have been sky high between fans and OM president Jacques-Henri Eyraud, who they say has been managing the club more like a company than as a soccer club since he took over in 2016.

Some supporters broke into the club’s training centre earlier this month during a protest against the president. Coach Andre Villas-Boas was suspended after offering to resign.

The board’s letter to the supporters’ group prompted criticism from the mayor of Marseille, Benoit Payan.

“The supporters are the soul of the club,” Payan wrote on Twitter. “This formal notice from the board is incomprehensible, it cannot be that tens of thousands fans pay for the action of a few persons who have already been brought to justice.

“I wrote to Jacques-Henri Eyraud to ask him to calm things down.”

Meanwhile, Eyraud told a business summit on Wednesday that the French league needs to be reduced in size as part of the post-COVID-19 recovery of the game.