The government is putting Britons at risk by depriving Isis members of their British citizenship, a former defence minister has said.

Tobias Ellwood told The Independent the detention of thousands of jihadis and their families in Syria was creating conditions for an Isis resurgence.

“We’ll see Daesh 2.0,” he warned. “We’ll see a repeat of al-Qaeda regrouping and becoming a very real threat, and that threat won’t just pose itself in the Middle East, but also to Britain.”

The former soldier, whose brother was killed in the 2002 Bali bombings, said more British victims had been killed in terror attacks abroad than in the UK.

“We’ve still got attacks taking place, we’ve still got the ideology alive,” said Mr Ellwood, who was sacked as defence minister by Boris Johnson.

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

“We’ve done well to stand up as a lead nation on the battlefield in defeating Daesh and the caliphate, but the last piece of the jigsaw is 20,000 or so fighters that nobody really wants.

“They will regroup to fight another day – we’re already seeing it.”

Mr Ellwood said the UK had not “concluded our mission” to defeat Isis, adding: “We need to complete it rather than allowing it to haunt us in the future.

“We stepped forward because we had a sense of duty, of values and standards, and if we just give up on that we’ve forgotten what we were fighting for.”

He spoke out after it emerged that Sajid Javid stripped Jack Letts of his British citizenship, as well as Shamima Begum and two members of the “Beatles” terror cell.

The move means the government will not repatriate them from Syria for trial, has cancelled their passports and would bar any attempted entry to the UK.

Bangladesh and Canada hit out at the government for “offloading Britain’s responsibilities” over Begum and Letts, who had publicly pleaded to return home.

They are among thousands of alleged Isis members detained by the Syrian Democratic Forces (SDF), whose pleas for the UK to take back its jihadis have so far been refused.

The Independent understands that dozens of British Isis members and at least 30 of their children are in custody.

As a foreign minister, Mr Ellwood attended meetings in 2015 and 2016 where international members of the US-led coalition drew up plans against Isis.

ISIS brides seen raising their index fingers in Stacey Dooley's Panorama documentary

“We talked about cutting off the financing, cutting off the online presence and recruitment, cutting off the connectivity and stopping the movement of people into Isis territory,” he recalled.

“The one thing we never did was then say, ‘OK, fine, when the caliphate finally falls and you get a mass exodus or surrender of people as you do in any fall of a regime, what is the process?’

“At the moment they’re just behind barbed wire with no process whatsoever and the SDF unable to manage it.”

Hundreds of Isis prisoners have already been released from jail in Syria after the Kurdish authorities holding them said they had “no blood on their hands”, and there are fears that more will be freed without any formal assessment of the danger they pose.

Abdel Karim Omar, a Kurdish foreign affairs official, told The Independent that thousands of detained Isis fighters, women and children are a “big burden”.

“They belong to 49 countries, and they don’t have documents and passports,” he said, speaking earlier this year.

“We cannot bear this responsibility alone. We ask the international community and the countries to which Isis members belong to take up its moral and legal duty and repatriate their citizens back to their countries.”

The British government has refused the call and has not yet proposed an alternative judicial process or long-term solution for the detainees.

Mr Ellwood said that in the early days of the battle against Isis, where the UK supported Kurdish forces on the ground with airstrikes, few prisoners of war emerged because fighters were either killed in battle or committed suicide attacks.

As Isis territory shrank, the US-led coalition vastly underestimated the number of people inside its remaining pockets of territory and did not prepare for the surrender of thousands of men, women and children in March.

Tens of thousands were crammed into the al-Hol refugee camp, where the black flag of Isis was raised in July.

The al-Hol camp in Syria (AP)

Mr Ellwood warned that the detention centre was “haemorrhaging” jihadis, amid bribery allegations, while those still inside were free to radicalise each other.

The Conservative MP, who was hailed a hero for his efforts to save the police officer murdered in the Westminster attack, said a new strategy was needed to deal with committed extremists who are willing to die for their cause.

He called on international leaders attending the UN General Assembly next month to find a solution, which could include a designated legal process for Isis members.

Isis claimed responsibility for a suicide attack that killed 80 people at a wedding in Afghanistan last week, and its propaganda channels churn out daily reports of executions, shootings, battles and bombings across the Middle East, Asia and Africa.

In the past two months, Isis has released more than a dozen videos showing factions in different countries renewing their pledges of allegiance to leader Abu Bakr al-Baghdadi.

“The afflictions and tribulations experienced by your brothers in [Syria] only made them more steadfast and patient,” said one fighter, following footage from Yemen, Bangladesh, Somalia, Tunisia, Libya, the Philippines, Turkey, Egypt the Caucasus and elsewhere.

A 2016 report commissioned by the government warned that removing extremists’ citizenship left them free to continue terrorist activities abroad, prevented monitoring and encouraged the “dangerous delusion that terrorism can be made into a foreign problem”.

But the use of the controversial power soared by more than 600 per cent in a year, and has been applied to more than 150 people since 2010.

A Home Office spokesperson said: “The home secretary has the power to deprive someone on conducive to the public good grounds of their British citizenship, where it would not render them stateless.

“Depriving someone of their British citizenship is never a decision that is taken lightly. Decisions are based on advice from officials, lawyers and the intelligence agencies and all available information to keep our country safe.