It is “not justice in any sense” to strip Isis fighters of their British citizenship rather than putting them on trial, the government has been told.

Diane Abbott, Labour’s shadow home secretary, said the UK has a duty to deal with Jack Letts and other captured jihadis itself.

“Whenever there are reasonable grounds to suspect that someone who is entitled to return to this country has either committed or facilitated acts of terrorism, they should be fully investigated and where appropriate prosecuted,” she told The Independent.

“We are not in favour of making people stateless, that’s a punishment without due process.

“Simply removing citizenship may please ministers, but it isn’t justice in any sense.

“Government ministers shouldn’t offload Britain’s responsibilities to other countries.”

Timeline of the Isis caliphate Show all 19 1 /19 Timeline of the Isis caliphate Timeline of the Isis caliphate ISIS began as a group by the merging of extremist organisations ISI and al-Nusra in 2013. Following clashes, Syrian rebels captured the ISIS headquarters in Aleppo in January 2014 (pictured) AFP/Getty Timeline of the Isis caliphate Abu Bakr Al-Baghdadi declared the creation of a caliphate in Mosul on 27 June 2014 Timeline of the Isis caliphate Isis conquered the Kurdish towns of Sinjar and Zumar in August 2014, forcing thousands of civilians to flee their homes. Pictured are a group of Yazidi Kurds who have fled Rex Timeline of the Isis caliphate On September 2 2014 Isis released a video depicting the beheading of US journalist Steven Sotloff. On September 13 they released another video showing the execution of British aid worker David Haines Timeline of the Isis caliphate The US launched its first airstrikes against Isis in Syria on 23 September 2014. Here Lt Gen William C Mayville Jnr speaks about the bombing campaign in the wake of the first strikes Getty Timeline of the Isis caliphate Isis militants sit atop a hill planted with their flag in the Syrian town of Kobani on 6 October 2014. They had been advancing on Kobani since mid-September and by now was in control of the city’s entrance and exit points AFP/Getty Timeline of the Isis caliphate Residents of the border village of Alizar keep guard day and night as they wait in fear of mortar fire from Isis who have occupied the nearby city of Kobani Getty Timeline of the Isis caliphate Smoke rises following a US airstrike on Kobani, 28 October 2014 AFP/Getty Timeline of the Isis caliphate YPG fighters raise a flag as they reclaim Kobani on 26 January 2015 VOA Timeline of the Isis caliphate Isis seized the ancient Syrian city of Palmyra on 20 May 2015. This image show the city from above days after its capture by Isis Getty Timeline of the Isis caliphate Kurdish forces are stationed on a hill above the town of Sinjar as smoke rises following US airstrikes on 12 November 2015 AFP/Getty Timeline of the Isis caliphate Kurdish forces enter Sinjar after seizing it from Isis control on 13 November 2015 AFP/Getty Timeline of the Isis caliphate Iraqi government forces make the victory sign as they retake the city of Fallujah from ISIS on 26 June 2016 Getty Timeline of the Isis caliphate Iraqi forces battle with Isis for the city of Mosul on 30 June 2017 AFP/Getty Timeline of the Isis caliphate Members of the Iraqi federal police raise flags in Mosul on 8 July 2017. On the following day, Iraqi prime minister Haider Al Abadi declares victory over Isis in Mosul Getty Timeline of the Isis caliphate Members of Syrian Democratic Forces celebrate in Al-Naim square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign Getty Timeline of the Isis caliphate Female fighters of the Syrian Democratic Forces celebrate in Al-Naim Square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign AFP/Getty Timeline of the Isis caliphate Trucks full of women and children arrive from the last Isis-held areas in Deir ez-Zor, Syria in January 2019 They were among the last civilians to be living in the ISIS caliphate, by this time reduced to just two small villages in Syria’s Deir ez-Zor Richard Hall/The Independent Timeline of the Isis caliphate Zikia Ibrahim, 28, with her two-year-old son and 8-month-old daughter, after fleeing the Isis caliphate, on Saturday 26 January 2019 Richard Hall/The Independent

Letts, a Muslim convert from Oxford, became known as “Jihadi Jack” after travelling to Syria in 2014.

Now 24, he was captured as he tried to flee to Turkey in May 2017 and has been charged by Kurdish authorities with being a member of Isis.

The British government has refused to repatriate Letts for trial and removed his UK citizenship, making him a sole Canadian national.

Ralph Goodale, Canada’s public safety minister, said: “Terrorism knows no borders, so countries need to work together to keep each other safe.

“Canada is disappointed that the United Kingdom has taken this unilateral action to offload their responsibilities.”

It remains unclear whether Canada is willing or able to prosecute Letts for terror offences, and politicians have reacted to the UK’s decision with outrage.

The row comes days before Boris Johnson is due to meet Justin Trudeau at the G7 summit in France.

Dominic Raab, the UK foreign secretary, met his Canadian counterpart Chrystia Freeland in Toronto earlier this month and discussed Letts.

Mr Goodale’s office said Canada was under no legal obligation to facilitate the return of Canadian citizens detained in Syria, adding: “We will not expose our consular officials to undue risk in this dangerous part of the world.”

John McKay, chair of the Canadian parliament’s committee on public safety and national security, called the British government “gutless”.

Jack Letts, seen here in Isis-controlled Tabqa in 2016

“This young man is entirely a British subject – he’s raised British, educated British, everything about him is British,” he told BBC Radio 4’s Today programme.

“The only remote connection he has to Canada is through his father, and frankly I don’t think it’s the way two allies should be treating each other.”

Mr McKay said Canada would not be able to prosecute Letts for joining Isis, adding: “Our legislation works on the assumption that you have to leave from Canada in order to be prosecuted for a terrorist offence, so we are unable to initiate any prosecution.”

Letts’ father, organic farmer John Letts, visited Canada last year to call for the country’s government to help his son leave Syria.

He said he found out his son’s British citizenship had been removed last month, and The Independent understands the decision was made under former home secretary Sajid Javid.

His father is Canadian but his mother, Sally Lane, is British and he was born and raised in the UK.

The pair were convicted of funding terrorism by sending their son £223 when they knew he was in Syria, but were spared jail in June.

They have maintained their own innocence and defended their son, vowing to lobby Canadian politicians to repatriate him.

In an interview with Channel 4, John Letts branded Mr Javid a “coward”, adding: “Obviously it’s his last act [as home secretary] and he can move on and not have to even justify it.

“I would love to have a debate with Sajid Javid about this and see what are the reasons they’ve done this, we can’t even find out, it’s all secret.”

John Letts told Canadian television the pair believe their son is “innocent” and want him to be able to prove it at trial.

John Letts and Sally Lane arrive at the Old Bailey in May (PA) (Yui Mok/PA)

“As far as I’m concerned, there is no evidence that Jack has done anything wrong,” he added.

Letts posted a photo of himself online in combat fatigues near Isis’s de facto capital of Raqqa, and openly wrote about his desire to carry out a terror attack on Facebook.

In an interview with ITV earlier this year, Letts described how he lived on the “Oxford Street of Raqqa” and had welcomed news of Isis’s 2015 Paris attacks.

He claimed he later realised he was an “idiot” and tried to escape Isis territory.

Speaking on Monday, Letts said the removal of his British citizenship made “no difference” to his situation.

“I’ve been here for two and a half years, they haven’t helped me at all,” he added. “It’s almost as if I’m not a British citizen anyway ... I don’t think anyone is going to help me.”

Kurdish authorities have urged Britain and other nations to “take up their moral and legal duty” to repatriate foreign fighters.

Three years ago, a government-commissioned review warned that stripping people of their citizenship may be an “ineffective and counterproductive weapon against terrorism”.

The document said the move left jihadis free to continue terrorist activities abroad, prevented monitoring and encouraged the “dangerous delusion that terrorism can be made into a foreign problem”.

The government has refused to repatriate Letts, Shamima Begum and dozens of other British jihadis imprisoned in Syria, while dramatically increasing its use of controversial powers to remove their British citizenship.

Some have allegedly been made stateless by the move, which is a violation of international law, although government guidance permits the move if a person is eligible for another nationality.

“Banishing people from the UK belongs in the dark ages – not 21st century Britain,” the Liberty campaign group said.

“The government has an array of powers, including the criminal law, which it can and should use to deal with people suspected of involvement in terrorism.”

Official statistics show citizenship deprivations were used only a handful of times a year, until they rocketed by 600 per cent from 14 people in 2016 to 104 in 2017.

The Home Office declined to give a reason for the dramatic increase, and said it could not provide a breakdown of how many Isis members were involved or the justification for each case.

A spokesperson said: “Decisions on depriving a dual national of citizenship are based on substantial advice from officials, lawyers and the intelligence agencies and all available information.