Two of the surviving journalists from French satirical weekly Charlie Hebdo have brushed off controversy over a literary award.

In January, 12 members of the magazine's staff were massacred when two Islamist gunmen - enraged by caricatures of the Prophet Mohammed - stormed an editorial meeting in Paris.

This month, the publication is to be honoured by the PEN authors association, but more than 150 writers, including Australian Peter Carey, have pulled out of the event in protest at cartoons they say are offensive to France's minority populations.

Speaking in Washington on Friday, Charlie Hebdo's film critic Jean-Baptiste Thoret - who only avoided the attack because he had been late for work - said the critics had misunderstood the reason for the PEN award.

"Maybe there is a little misunderstanding, I guess they imagine this award was given to Charlie Hebdo regarding its content," he said.

"There is a confusion. It's an award given to the principle of freedom of speech."

Those pulling out of the May 5 annual PEN American Center gala include celebrated writers such as Michael Ondaatje, Francine Prose, Teju Cole, Rachel Kushner, Taiye Selasi and Carey.

Carey, a two-time Booker Prize winner, said the award went beyond the group's traditional role of protecting freedom of expression against government oppression.

"A hideous crime was committed, but was it a freedom-of-speech issue for PEN America to be self-righteous about?" the New York Times quoted him as saying.

"All this is complicated by PEN's seeming blindness to the cultural arrogance of the French nation, which does not recognise its moral obligation to a large and disempowered segment of their population."

Charlie's editor-in-chief Gerard Biard dismissed this argument.

"It's always gratifying to have a contrarian opinion, to say 'I don't think like the masses. I'm above all that'," he told AFP.

"That's their problem. If they think PEN is no longer about protecting free expression, why don't they leave it?"

Speaking at Freedom House, a democratic rights watchdog, Thoret pointed out that out of 500 Charlie Hebdo cover stories published before the attack, only 11 dealt with Islam.