The affair is increasingly embarrassing for Denmark’s intelligence services and the government has repeatedly rejected calls for an inquiry.
Samsam says he was working for Denmark’s secret service PET and military intelligence service FE in Syria in 2013 and 2014, spying on foreign jihadist fighters.
Several investigations by Danish media have backed him up, concluding the 34-year-old Dane of Syrian origin never joined IS.
But the two intelligence agencies have refused to say whether he was working for them.
Samsam, who has a long criminal record, travelled to Syria in 2012 of his own accord to fight the regime.
Danish authorities investigated him after his return but did not press any charges.
He was then sent to the war zone on several occasions with money and equipment provided by PET and later FE, according to Danish media outlets DR and Berlingske.
They based their reports on anonymous witnesses and money transfers wired to Samsam.
In 2017, threatened by Copenhagen thugs in a settling of scores unrelated to his trips to Syria, Samsam headed to Spain.
There, he was arrested by Spanish police, who were surprised to find pictures of him on Facebook posing with the IS flag.
Samsam was sentenced the following year to eight years in prison for having joined IS.
“When he was arrested in Spain in 2017 he was 100 percent sure that he was going to be helped by Danish authorities”, his lawyer in Denmark Erbil Kaya told AFP.
But the Danes never intervened.
“It’s very difficult to prove you’ve been an agent. It’s not like he has a payslip or employment contract”, said Kaya.
Samsam has been serving his sentence, since commuted to six years, in Denmark since 2020.
Last year, he filed a lawsuit against Denmark’s intelligence services to force them to acknowledge his role with them.
The case is due to be heard in August.
“It’s very rare to leave an agent to serve a long prison sentence”, Magnus Ranstorp, a terrorism expert and research director at the Swedish Defence University, told AFP.
He said the fact that Samsam was arrested in Spain may have complicated his situation.
In a case like this, “an intelligence service would prefer to sweep this under the rug”, Ranstorp said.
“These are things that can’t be exposed in court. Even if the agent is no longer of any use, he shouldn’t attract any attention.”
During last year’s election campaign, Danish politicians across the board said they wanted an official inquiry.
But the new left-right government in power since December has rejected it.
“To protect our open society and democracy, it is essential that nothing that concerns the intelligence services be revealed”, the justice ministry told AFP.
Samsam’s lawyer Kaya condemned the government’s stance as “incomprehensible”.
Samsam “has the impression that the authorities don’t want to help him and are doing everything to hide the truth, he added.
“The truth will be revealed one day and I think this case will be called our ‘Dreyfus affair'”, the lawyer said, referring to the French criminal justice scandal at the turn of the 20th century.
Samsam recently went on a one-week hunger strike from his prison cell to protest “the inhumane conditions of his imprisonment”.
In December, the two intelligence services said they never divulged the identity of informants “both for the sake of the sources themselves and for the services’ operations”.
Being an informant or agent does not grant immunity from conviction if illegal acts have been committed.
“Deny, deny, deny! That’s the golden rule for these services. They never reveal their sources or their methods”, said Ranstorp.
The case was “harmful to their reputation, but they’ll survive it”, he said.
Several Danish opposition parties are still calling for an investigative commission.
And like with any good spy story, a movie is in the works.