A young man from Oxford who became known as 'Jihadi Jack' after he travelled to Syria has not been heard from since July and has been tortured by anti-IS forces, his parents claim.
Jack Letts has not made contact with his parents since July this year after he was taken prisoner by Kurdish milita during his escape from the former ISIS stronghold of Raqqa.
The 21-year-old Muslim convert has ceased contact with his parents after last telling them he was intending to carry out a "protest". In the same audio message he said the act "might get him shot".
His middle-class parents have revealed a series of texts and audio messages which detail his experience after being captured by Kurdish forces, the Mail on Sunday reported.
John and Sally Letts, who undertook a week-long hunger strike to highlight their son's situation, say he was forced to endure long periods of solitary confinement, starved of food and tortured.
The couple also claim that Letts was only recieving one meal a day.
Mrs Letts, 55, said: "We have not heard a peep from him since July 8."
On Saturday, Letts' captors released a statement saying he had been charged with being an Isis member, but his case was still "under investigation". The statement added that Letts was in weekly contact with his parents and was being well treated.
Mrs Letts said: "That's rubbish, a blatant lie and it discredits all their other claims."
The Kurdish security force holding Letts, known as the Asayish, has been condemned by NGO Human Rights Watch for holding prisoners without charge in poor conditions.
Speaking to his parents, Letts claimed that he "could prove" that he was being tortured with electricity. He also claimed his captors told him British officials fed them questions - suggesting that the UK government knew of his whereabouts and who was holding him.
His father John, 57, an organic farmer and botanist, said that the couple would accept their son should be detained and questioned if he returns to the UK. He said if the evidence merits it then Letts should be charged with an offence.
Both his parents acknowledged that a court might find that merely travelling to ISIS territory constituted to a crime, and would test his claims that he did not share the terror group's mantra.
Letts converted to Islam after suffering mental health issues which disrupted his schooling and left school at aged 16.
He was brought up in an affluent neighbourhood in Oxford and at first his parents said that his discovery of faith meant he had "new purpose".
Letts travelled to Syria in 2014 after attempting to study Arabic in Kuwait in May of the same year, then disappeared.