Young men who leave their homes to fight for terrorist groups in Syria mainly come from disadvantaged backgrounds, have low levels of education and “lack any basic understanding of the true meaning of jihad or even the Islamic faith”, according to a new report.

A study for the United Nations Office of Counter-Terrorism found that despite claiming to protect Muslims, most of the returned fighters were “novices” in their religion and some did not know how to pray properly.

“Most saw their religion in terms of justice and injustice rather than in terms of piety and spirituality,” said the authors of the report, which was based on interviews with 43 people from 12 countries.

They found that a typical fighter “is most likely to be male, young and disadvantaged economically, educationally, and in terms of the labour market”.

“He is also more likely than not to come from a marginalised background, both socially and politically,” the reported added.

“Most were unemployed, or underemployed, and/or said that their life lacked meaning.”

Three quarters of those interviewed reached Syria but subsequently decided to leave, while others were intercepted by authorities in their own country or stopped en route.

Thousands of British Muslims gather to denounce Isis and call for 'peaceful caliphate'

Despite an appeal to all UN member states, the authors expressed regret that only seven countries agreed to participate in the study - three from the EU and four from the Middle East and North Africa.

Professor Hamed el-Said, of Manchester Metropolitan University, and terrorism expert Richard Barrett met most of the returnees in prison or under the watchful eye of security services.

The majority of interviewed fighters, who attempted to join groups including Isis, al-Qaeda affiliate Jabhat al-Nusra and jihadi Ahrar al-Sham, came from large and dysfunctional families in deprived parts of cities where they were “isolated from mainstream social, economic and political activity”.

“Religious belief seems to have played a minimal role in the motivation of this sample,” the report found, saying economic factors had become more important as terrorist groups promised wages, homes and even wives.

The findings supported previous research using leaked Isis documents, which showed that most recruits profess to have only a “basic” knowledge of Sharia law, and warnings of a growing “crime-terror nexus” seeing violent criminals travel to Syria in the hope of “redemption”.

Following the declaration of the so-called Islamic State in 2014, the group produced a huge amount of propaganda seeking to attract Muslims with the promise of life free of supposed Western oppression, lived in comfort and peace.

Rose-tinted videos sought to present a utopian existence, showing smiling militants engaging in activities like bee-keeping, farming and even pizza-making as Western fighters used Twitter to broadcast images of palatial homes, swimming pools and expensive cars provided by the “caliphate”.

Timeline: The emergence of Isis Show all 40 1 /40 Timeline: The emergence of Isis Timeline: The emergence of Isis 2000 Abu Musab al-Zarqawi (pictured here) forms an al-Qaeda splinter group in Iraq, al-Qa’eda in Iraq. Its brutality from the beginning alienates Iraqis and many al-Qaeda leaders. Timeline: The emergence of Isis 2006 Al-Zarqawi is killed in a U.S. strike. Al-Zarqawi’s successor, Abu Ayyub al-Masri, announces the creation of the Islamic State in Iraq (ISI). Reuters Timeline: The emergence of Isis 2009 Still al-Qaeda-linked ISI claims responsibility for suicide bombings that killed 155 in Baghdad, as well as attacks in August and October killing 240, as President Obama announces troop withdrawal from Iraq in March. Getty Images Timeline: The emergence of Isis 2010 Abu Bakr al-Baghdadi becomes head of ISI, at lowest ebb of Islamist militancy in Iraq, which sees last U.S. combat brigade depart. Timeline: The emergence of Isis 2012 In Syria, protests (pictured here starting in Daree) have morphed into what president Assad labelled a “real war” with emergence of a coalition of forces opposed to Assad’s regime. Syria group Jabhat al-Nusra are among rebel groups who refuse to join, denouncing it as a “conspiracy”. Bombings targeting Shia areas, killing more than 500 people, spark fears of new sectarian conflict. Sunni Muslims stage protests across country against what they see as increasingly marginalisation by Shia-led government. AP Timeline: The emergence of Isis 2013 Al-Baghdadi renames ISI as the Islamic State in Iraq and Syria, or Isis, as the group absorbs Syrian al-Nusra, gaining a foothold in Syria. In response, al-Qaeda chief Ayman al-Zawahiri (Bin Laden’s successor) concerned about Isis’ expansion orders that Isis be dissolved and ISI operations should be confined to Iraq. This order is rejected by al-Baghdadi. AFP Timeline: The emergence of Isis 2014 - January Isis fighters capture the Iraqi cities of Fallujah and Ramadi, giving them base to launch slew of attacks further south. AP Timeline: The emergence of Isis 2014 - June Isis declares itself the Caliphate, calling itself Islamic State (IS). The group captures Mosul, Iraq’s second largest city; Tal Afar, just 93 miles from Syrian border; and the central Iraqi city of Tikrit. These advances sent shockwaves around the world. Timeline: The emergence of Isis 2014 - June Around the same time Isis releases a video calling for western Muslims to join the Caliphate and fight, prompting new evaluations of extremists groups social media understanding. Timeline: The emergence of Isis 2014 - June Isis take Baiji oil fields in Iraq - giving them access to huge amounts of possible revenue. EPA Timeline: The emergence of Isis 2014 - August James Foley is executed by the group as concerns grow for second American prisoner, fellow reporter Steven Sotloff. AP Timeline: The emergence of Isis 2014 - August Obama authorises U.S. airstrikes in Iraq, helping to stall Isis’ along with action by Kurdish forces following the deaths of hundreds of Yazidi people on Mount Sinjar. Timeline: The emergence of Isis 2014 - September Isis release video showing Steven Sotloff’s murder prompting Western speculation his executioner is same man who killed Mr Foley. EPA Timeline: The emergence of Isis 2014 - September Obama tells us that America “will hunt down terrorists who threaten our country” EPA Timeline: The emergence of Isis 2014 - September Isis release a video appearing to show David Haines, who was captured by militants in Syria in 2013, wearing an orange jumpsuit and kneeling in the desert while he reads a pre-prepared script. It later shows what appears to be the aid worker's body. Rex Timeline: The emergence of Isis 2014 - September Peshmerga fighters scrabble to hold positions in the Diyala province (a gateway to Baghdad) as Isis fighters continue to advance on Iraqi capital. AFP Timeline: The emergence of Isis 2014 - October Aid worker Alan Henning is killed. Self-imposed media blackout refuses to show images of him in final moments, instead focuses upon humanitarian care. AP Timeline: The emergence of Isis 2014 - October Isis raise their flag in Kobani, which had been strongly defended by Kurdish troops. The victory goes against hopeful western analysis Isis had overextended itself, while alienating much of the Muslim population through the murder of Henning. Victory causes fresh waves of Kurdish refugees arriving in Turkey. Timeline: The emergence of Isis 2014 - November American hostage, who embarced values of Islam, Peter Kassig and 14 Syrian soldiers are shown meeting the same fate as other captives. But intelligence agencies will be poring over the apparently significant discrepancies between this and previous films. Seramedig.org.uk Timeline: The emergence of Isis 2015 - February Isis has released a video revealing the murder by burning to death of a Jordanian pilot held by the group since the end of December 2014. Reuters Timeline: The emergence of Isis 2015 - February Isis militants have released videos which appear to show the beheading of Japanese hostages Haruna Yukawa and Kenji Goto. Timeline: The emergence of Isis 2015 - February American aid worker, Kayla Mueller was the last American hostage known to be held by Isis. She died, according to her captors, in an airstrike by the Jordanian air force on the city of Raqqa in Syria, though US authorities disputed this. AP Timeline: The emergence of Isis 2015 - February Isis militants have posted a gruesome video online in which they force 21 Egyptian Coptic Christian hostages to kneel on a beach in Libya before beheading them. Egypt vowed to avenge the beheading and launched air strikes on Isis positions. AP Timeline: The emergence of Isis 2015 - February The British Isis militant suspected of appearing in videos showing the beheading of Western hostages has been named in reports as Mohammed Emwazi from London. Rex Features Timeline: The emergence of Isis 2015 - March Isis triple suicide attack has killed more than 100 worshippers and hundreds of others were injured after the group members targeted two mosques in the Yemeni capital of Sanaa. AP Timeline: The emergence of Isis 2015 - April Iraqi forces have claimed victory over Isis in battle for Tikrit and raised the flag in the city. EPA/STR Timeline: The emergence of Isis 2015 - April Isis has claimed responsibility for a suicide bomb attack in Afghanistan that killed at least 35 people queuing to collect their wages and injured 100 more. EPA Timeline: The emergence of Isis 2015 - April Isis’ media arm released a 29-minute video purporting to show militants executing Ethiopian Christians captives. The footage bore the extremist group’s al-Furqan media logo and showed the destruction of churches and desecration of religious symbols. A masked fighter made a statement threatening Christians who did not convert to Islam or pay a special tax. Timeline: The emergence of Isis 2015 - May Abu Bakr al-Baghdadi, the leader of Isis has been "incapacitated" by a spinal injuries sustained in a US air strike in Iraq. He is being treated in a hideout by two doctors from Isis’ stronghold of Mosul who are said to be "strong ideological supporters of the group". Timeline: The emergence of Isis 2015 - May Isis has also claimed responsibility for killing 300 of Yazidi captives, including women, children and elderly people in Iraq AP Timeline: The emergence of Isis 2015 - May Isis attack on Prophet Mohamed cartoon contest in Texas was its first action on US soil. Two gunmen were shot and killed after launching the attack at the exhibition. Elton Simpson and Nadir Soofi have been named as the attackers at the Curtis Culwell Centre arena in Garland. Timeline: The emergence of Isis 2015 - May Isis’s deputy leader, Abu Alaa Afri, a former physics teacher who was thought to have taken charge of the deadly terrorist group, has been killed in a US-led coalition airstrike. Timeline: The emergence of Isis 2015 - May US special forces have killed a senior Isis leader named as Abu Sayyaf in an operation aiming to capture him and his wife in Syria. Getty Images Timeline: The emergence of Isis 2015 - May Iran-backed militias are sent to Ramadi by the Iraqi government to fight Isis militants who completed their capture of the city. Government soldiers and civilians were reportedly massacred by extremists as they took control and the army fled. Charred bodies were left littering the city streets as troops clung on to trucks speeding away from the city. Ramadi is the latest government stronghold to fall to the so-called Islamic State, despite air strikes by a US-led international coalition aiming to stop its advance in Iraq and Syria. AFP Timeline: The emergence of Isis 2015 - May Isis rounded up civilians trapped in Palmyra and forced them to watch 20 people being executed in the historic city’s ancient amphitheatre. The Unesco World Heritage site was overrun by militants, threatening the future of 2,000 year-old monuments and ruins. Thousands of Palmyra’s residents fled but many are still living within the city walls, while the UN human rights office in Geneva said it had received reports of Syrian government forces preventing people from leaving until they retreated from the city. Getty Timeline: The emergence of Isis 2015 - May A group of Isis-affiliated fighters have captured a key airport in central Libya. The militants took control of the al-Qardabiya airbase in Sirte after a local militia tasked with defending the facility withdrew from their positions. Affiliates of Isis, already control large parts of Sirte, the birthplace of former Libyan leader Muammar Gaddafi and a former stronghold of his supporters. Timeline: The emergence of Isis 2015 - June The US Air Force has destroyed an Isis stronghold after an extremist let slip their location on social media. According the Air Force Times, General Herbert "Hawk" Carlisle, commander of Air Combat Command, said that Airmen at Hulburt Field, Florida, used images shared by jihadists to track the location of their headquarters before destroying it in an airstrike. Reuters Timeline: The emergence of Isis 2015 - June Kurdish forces captured a key military base in a significant victory in Raqqa as well as town of Tell Abyad. YPG fighters, backed by US-led airstrikes and other rebels, consolidated their gains, when they seized the key town on the Syria-Turkey border. They are now just 30 miles to the north of Raqqa and have cut off a major supply route deep inside Isis-held territory. Ahmet Silk/Getty Timeline: The emergence of Isis 2015 - June Isis has released gruesome footage claiming to show the murder of more than a dozen men by drowning, decapitation and using a rocket-propelled grenade as it seeks to boost morale among its fanatical supporters. Timeline: The emergence of Isis 2015 - June Isis has begun carrying out its threat to destroy structures in the ancient Syrian city of Palmyra, blowing up at least two monuments at the Unesco-protected site as Syrian government troops made advances on the Islamist’s positions. AFP

The UN report said the propaganda exerted a powerful pull on young men who feel they have little prospects at home, especially when combined with perceived grievances and a wish to protect Sunni Muslims in areas of Syria targeted by Bashar al-Assad’s government.

“For some, this sense of brotherhood was reinforced by a sense of religious obligation,” it said.

“The respondents of this survey claimed they did not go to Syria with the intention of becoming a terrorist, nor did they return with that purpose in mind.”

Despite the role of propaganda sparking a global crackdown on extremist online activity, the report found that among surveyed fighters, the internet played “a far less significant role as an independent source of radicalisation than is generally assumed, and certainly a far less significant role than real life contact”.

The authors found that would-be jihadis went online to confirm and strengthen ideas that were already taking root, adding: “The internet then played a key role in reinforcing a decision that had in part been taken already.”

Far more important was friendship circles and social networks formed around mosques, prisons, schools, universities, neighbourhoods or the workplace – a conclusion supported by the high number of known British militants who were part of radical networks or left the country with friends and relatives.

The UN report said identity politics played a key role in radicalisation, warning of “significant policy implications" arising from perceived injustice and discrimination.

It added: “Bad governance, especially disregard for the rule of law, discriminatory social policies, political exclusion of certain communities…harassment by the security authorities, and confiscation of passports or other identity documents, all contribute to feelings of despair, resentment, and animosity towards the government and provide fertile ground for the terrorist recruiter.”

Mehdi Hassan, also known as Abu Dujana, is one of many British fighters who joined Isis with friends - in his case the 'Britani Brigade Bangladeshi Bad Boys', who have all been killed (Twitter)

Although their accounts are highly unreliable, several imprisoned former Isis members have blamed the security services for their radicalisation.

Harry Sarfo, a German-born militant who grew up in the UK and joined Isis for three months in 2015, told The Independent his experience of police raids and harassment from the local community after he fell under suspicion as an extremist drove him to Syria.

“My friend kept on telling me: ‘This is what you get for being Muslim in the West, especially Germany. You are black and Muslim, your wife is covered, what do you expect? They think you are a bloody terrorist. You should go and live in the Islamic State, where every Muslims’ rights are protected. Life for you here is over,” he recalled. “At the time, everything he said made sense.”

Similar concerns have been raised about the Government’s controversial Prevent strategy, which is viewed by some to be divisive and discriminatory, while Isis itself has been attempting to capitalise on air strikes on its territory by publishing graphic images of dead children alongside calls for global terror attacks.

As Isis has been pushed back in Iraq and Syria, routes to its territories have shut down and the group’s calls have largely switched from calling on supporters to travel to the “caliphate”, to inciting attacks in their home countries across the West.

Some analysts say the failure of Isis’ state project will dent its lure to potential recruits, although the fighters in the UN’s sample found themselves “disillusioned” by the group even at its peak.

The report said they left Syria because of their “genuine disappointment in and disenfranchisement by the terrorist organisation they joined”, feeling alienated by the group and local Syrians, the deaths of friends or calls by loved ones to come home.

They authors hope the research will help countries around the world to improve counter-extremism programmes that prevent people from considering joining Isis and other terrorist groups, as well as safely reintegrating those returning from the group’s shrinking territories.

Harry Sarfo is imprisoned in Germany, where he is under a new investigation for taking part in a mass execution

With an estimated 25,000 foreign fighters from more than 100 countries travelling to Syria, concern has been mounting over a potential influx of jihadis as Isis loses territory including its de-facto capital of Raqqa.

The city is completely sealed off and under heavy bombardment by the US-led coalition, and Isis is known to kill anyone caught attempting to defect, leading analysts to expect the number of recruits managing escape to be small.

“Not all returnees present the same degree of threat,” the UN report found, warning against treating all former fighters as high risk and “thereby radicalising those who are low threat through unwarranted persecution.”

​Prof el-Said and Mr Barrett argued that some ex-terrorists could become powerful voices against the groups they once joined, adding: “Governments will need to screen their returnees to identify the more dangerous among them as well as to select credible and trustworthy individuals who could counter recruitment narratives.”

Isis is currently intensifying its efforts to discredit defectors and featured Sarfo in a recent propaganda magazine decrying “fools who strayed” and spread “lies and falsehoods”.

While returned foreign fighters have been among Europe’s deadliest terrorists, including the “super cell” that carried out the Paris and Brussels attacks – the threat from supporters of the group who have been prevented from realising their desire to travel to Syria is increasing.

London Bridge ringleader Khuram Butt, Normandy church attacker Abdel-Malik Petitjean and Michael Zehaf-Bibeau, who shot a Canadian soldier dead outside the country’s war memorial, are among failed foreign fighters who chose to launch attacks on home soil instead.

“It is important at least not to underestimate the motivations and determination of those who failed to make it to Syria,” the report concluded.

“There is little room for complacency, but while the risk presented by returning foreign terrorist fighters is a real one, it should not be exaggerated.