Didier François was held prisoner for more than 10 months by the militant group before he was released in April last year.
In an interview with CNN's Christiane Amanpour, Mr François has described how his captors would speak to prisoners of their beliefs, but said the discussion was based on politics, rather than religion.
He said: "It was more hammering what they were believing than teaching us about the Koran. Because it has nothing to do with the Koran.
Fighters from ISIS marching in Raqqa, Syria (AP) Fighters from ISIS marching in Raqqa, Syria (AP)
"They didn't even have the Koran; they didn't want even to give us a Koran."
The comments come as Isis on Wednesday released video footage revealing the murder by burning to death of a Jordanian pilot held by the group since the end of December.
Authorities in Jordan have today said they have executed two militants, including a female prisoner sought by Isis, following the release of the video, which appeared to show pilot Muath al-Kasaesbeh being set on fire as he stood in a cage.
Jordanian pilot Muath al-Kasaesbeh (MUHAMMAD HAMED/Reuters) Jordanian pilot Muath al-Kasaesbeh (MUHAMMAD HAMED/Reuters)
The fate of Mr Kasaesbeh, a member of a large tribe that forms the backbone of support for the country's Hashemite monarchy, has gripped Jordan for weeks, Reuters news agency has reported. Some Jordanians have criticised King Abdullah for embroiling them in US-led air strikes in Syria, which they said would provoke a backlash by militants
The king cut short a visit to the US to return home following word of Mr Kasaesbeh's death. In a televised statement, he said the pilot's killing was an act of "cowardly terror" by a deviant group that had no relation to Islam.
Mr François, who was held for months with James Foley, has previously suggested he has a "rough idea" as to the identity of the American's suspected British killer.