Followers of the Three Lions were involved in serious disturbances in the historic port city ahead of England's 1-1 draw with Russia at the Stade Velodrome on Saturday, when more trouble took place in the stands after the final whistle.
Both teams have been threatened with expulsion from the tournament by UEFA if further violence occurs.
A long history of hooliganism has seen English fans condemned by many as typical perpetrators of such disorder, but numerous witnesses claim they were instead the victims of premeditated aggression, including prominent fan rights advocates FSF.
"What we can say with confidence is that to the best of our knowledge, none of the many violent incidents that took place in Marseille during our time there were initiated by England fans," the organisation said in a statement.
"We have witnessed groups coming together – sometimes Russian hooligans, sometimes Marseille ultras, sometimes simply gangs of local youths – with the deliberate aim of attacking England fans ... all of them have been intent on starting trouble and initiating violence.
"The attacks have often been brutal, and in that context, we can hardly condemn those England fans who were left with little option but to defend themselves and in some cases their families.
"The media talk of 'clashes' between fans, as if there were two groups determined to confront each other. That wasn't what happened here."
French police have come under criticism for their heavy-handed approach to any flashpoints, as local riot forces prioritise the disbursement of unruly crowds with the use of tear gas, rather than following pre-emptive tactics.
"That these attacks were allowed to happen at all raises crucial questions about the role of the French police," the FSF statement continued.
"If they can see a potential problem developing before their eyes, why do they do nothing to stop them getting near their target?"
FSF also questioned the suitability of Russia to host the World Cup in 2018 after their supporters appeared to charge England fans and neutral spectators alike in a poorly segregated stand after the match in Marseille.
The organisation said: "If Russia wants to be taken seriously as a football nation, competing in and indeed even hosting major international tournaments, then surely there has to be some serious action taken within Russia to stop their thug element carrying out these cowardly violent attacks?
"As things stand now, the prospect of a World Cup in Russia looks less appealing than ever."