Jack Letts, the 23-year-old Muslim convert from Oxfordshire, who declared himself an "enemy of Britain" and fled to the Middle East to join IS, has been stripped of his UK citizenship, The Daily Mail said in the report.
Letts was filmed among dozens of fellow IS prisoners, all in orange jumpsuits, who have been captured by Kurdish militia.
On Saturday night, his mother Sally Lane pleaded for Letts to be allowed to return and face trial in the UK so that he can be rescued from the conditions in which he was being held, but the Home Office has dismissed her plea.
Seeing the first images of Letts since he was taken prisoner two years ago, she told The Mail on Sunday: "It's heart-rending to see your son like this and to feel so completely powerless.
"We have been pressing the Red Cross for months to tell us what the jail is really like, but they always refuse, saying that to release this information would jeopardise their access."
Letts left Britain for the brutal 'caliphate' run by the IS terror group in 2014.
He has denied being a fighter. After denouncing IS as "un-Islamic" in social media posts, he managed to escape from the caliphate's capital Raqqa in May 2017.
Since then he has been held by the Kurdish YPG militia at the prison believed to be in the city of Qamishli. He has not been charged or put on trial.
In occasional letters to his parents sent via the Red Cross, Letts has described how he was being held in a mass cell, with almost no furniture, boiling in summer and freezing in winter, with no access to exercise or the outdoors, and little opportunity to wash.
Home Secretary, Chancellor Sajid Javid revoked Jack's UK citizenship earlier this year. Letts however, is still a citizen of Canada, where his father comes from.
Security sources have revealed that more than 60 British jihadis were languishing in Kurdish custody in northern Syria, The Daily Mail reported.
The male jihadis were being kept in secret prisons, while the women and children were in camps such as Roj, Al-Hol and Ayn Issa.
( With inputs from IANS )