A founder of the satirical French magazine Charlie Hebdo has accused its editor, who was killed by masked gunmen last Wednesday, of “dragging the team” to death by publishing provocative cartoons of the Prophet Mohamed.

Henri Roussel, 80, who contributed to the first issue in 1970 when the magazine was known as Hara-Kiri Hebdo, had written to editor Stéphane Charbonnier – who goes by the name “Charb” – to say of the divisive drawings: “I really hold it against you.”

Referring to the editor’s decision to print a drawing of Prophet Mohamed on the front cover in 2011, Mr Roussel – who publishes under the pen name Delfeil de Ton – wrote in this week's French magazine Nouvel Obs: “What made him feel the need to drag the team into overdoing it?”, The Telegraph reported.

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The cover of the magazine consisted of a drawing of Prophet Mohamed, which said “100 lashes of the whip if you don’t die laughing!” under a banner saying “Charia Hebdo” in reference to Sharia law. Soon afterwards, the magazine’s offices were burned down in a firebomb attack by arsonists who have not been identified.

Charlie Hebdo is extending its print run to five million copies for the “survivor’s issue” from the normal number of around 60,000. The first print run sold out in hours in France while people queued in long lines to wait their turn to buy copies.

Delfeil adds: “I believe that we are fools who took an unnecessary risk. That’s it. We think we are invulnerable. For years, decades even, it was a provocation and then one day the provocation turns against us.

“He shouldn’t have done it, but Charb did it again a year later, in September 2012.”

Charlie Hebdo: The first edition since the Paris massacre Show all 15 1 /15 Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo The latest edition of Charlie Hebdo magazine, featuring a cartoon of the Prophet Mohamed on the front cover Getty Images Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo The first edition of Charlie Hebdo after 12 people were massacred at its offices AFP/Getty Images Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo A woman reads the first edition of Charlie Hebdo after 12 people were massacred at its offices AFP/Getty Images Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo As people march in Paris and the Arc de Triomphe displays the slogan 'Paris is Charlie', the tomb of the unknown soldier says "I have an erection!" AFP/Getty Images Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo A cartoon showing the Christian, Jewish and Muslim religions carving up the world, mirroring the post-war Yalta Conference between Stalin, Churchill and Roosevelt. The Catholic figure says he will guard the West and directs the Jewish figure to guard the East. AFP/Getty Images Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo What future for our jihadists? 'Security guard at Carrefour?' AFP/Getty Images Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo A man pays for his new Charlie Hebdo edition at a newsstand in Paris Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo People browse a newsstand advertising "We don't have any more Charlie Hebdo". Charlie Hebdo's defiant new issue sold out before dawn around Paris, with scuffles at kiosks over dwindling copies of the paper Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo People wait to buy the latest issue of Charlie Hebdo newspaper at a newsstand in Rennes Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo People wait outside a newsagents in Paris Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo A sign which translates as "Charlie Hebdo - Sold Out - Next deliveries on Thursday, Friday and Saturday" is displayed at a newsagents in Strasbourg Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo The depiction of the Prophet Mohamed on the front cover has offended many Muslims AP Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo People wait outside a newsagents in Dunkirk for a copy of the magazine AFP Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo Members of the public queue at a newspaper kiosk, where copies of the latest edition of Charlie Hebdo magazine are being sold in Paris Getty Charlie Hebdo: The first edition since the Paris massacre Charlie Hebdo The new edition of Charlie Hebdo is prepared for delivery at a press distribution center in the suburb of Marne La Valle in Paris

An issue a year after the firebomb attacks showed the Prophet in a wheelchair saying “You must not mock”. Another cartoon inside the magazine depicted him without clothes.

Brothers Cherif and Said Kouachi, and another man Amedy Coulibaly, were shot dead at the end of a three-day siege after they murdered a total of 17 people in Paris and they were reportedly heard shouting “we have avenged Prophet Mohamed!” A video purportedly from al-Qaeda in Yemen said it planned the attack.

However, the claims made by the magazine’s founder angered Charlie Hebdo lawyer Richard Malka, who has worked for the publication for the past 22 years.

He told Mathieu Pigasse, one of the owners of Nouvel Obs and Le Monde: “Charb has not yet even been buried and Obs finds nothing better to do that to publish a polemical and venomous piece on him.

“The other day, the editor of Nouvel Obs, Matthieu Croissandeau, couldn’t shed enough tears to say he would continue the fight. I didn’t know he meant it this way. I refuse to allow myself to be invaded by bad thoughts, but my disappointment is immense.”