A spokesperson for Britain’s interior ministry declined to confirm the report, noting it does not routinely comment on individual cases.
“Decisions on depriving a dual national of citizenship are based on substantial advice from officials, lawyers and the intelligence agencies and all available information,” the spokesperson said.
“This power is one way we can counter the terrorist threat posed by some of the most dangerous individuals and keep our country safe.”
However, the office of Canada’s Public Safety Minister Ralph Goodale did confirm that “the United Kingdom revoked the citizenship of Jack Letts”, and expressed disappointment at the move.
“Canada is disappointed that the United Kingdom has taken this unilateral action to offload their responsibilities,” the statement said.
“Terrorism knows no borders, so countries need to work together to keep each other safe”.
Letts was captured by Kurdish forces in Syria and is languishing in jail there, despite saying in a media interview earlier this year he would like to return to Britain.
“I’m not innocent,” he told ITV News. “I deserve what comes to me. But I just want it to be … appropriate … not just haphazard, freestyle punishment in Syria.”
Letts converted to Islam at the age of 16 and fled his home in Oxfordshire, central England, two years later to join IS.
His Canadian father and British mother were convicted in a UK court in June of funding terrorism by sending him a small amount of money during his time in Syria, but were spared jail.
The Mail on Sunday also reported that there were concerns that the issue could overshadow a meeting between Canadian Prime Minister Justin Trudeau and Britain’s new leader Boris Johnson at the G7 summit in France next weekend.
The decision is the latest instance of Britain revoking the citizenship of its nationals who went to join the Islamic State group’s self-proclaimed caliphate.
In February it faced criticism after stripping Shamima Begum, a teenager who travelled to Syria to marry an IS fighter, of her British citizenship.