Radicalised asylum seekers have murdered or injured more than 1,000 people in terror attacks in Europe since 2014, a new report has revealed.

In the past four years, 32 Islamist plots have involved those who had sought sanctuary – or 16 per cent. Three of the potential atrocities were in the UK, including Parson Green tube bomber Ahmed Hassan.

An analysis by academics found 44 refugees had either carried out atrocities or been thwarted before they could bring bloodshed to the streets.

The findings echo warnings by law enforcement chiefs that some so-called Islamic State fanatics who are bent on murder posed as refugees fleeing war and persecution. It was claimed they exploited the migrant crisis by pretending to be asylum seekers to sneak into Europe and cause carnage.

Terror expert Robin Simcox, of the Heritage Foundation think-tank in Washington DC, said it was 'disturbingly simple' for jihadists to hide among genuine refugees because the Continent's borders were under huge strain.

Munir Muhammed (pictured) was jailed for life after plotting a bomb campaign

European leaders had 'inadvertently increased the terrorist threat' as a direct result of their 'catastrophic' handling of controversial immigration and open-border policies.

He singled out German Chancellor Angela Merkel who sparked fury by throwing open the doors to Syrian refugees, leading to an influx of more than one million people in 2015.

It raised concerns that undercover jihadists were able to make their way across Europe unhindered once they had made it to the EU's passport-free Schengen zone, ending up in northern France in a bid to reach the UK.

Mr Simcox made clear that the fault for 11 successful attacks involving asylum seekers, which killed 182 people and injured 814, lay with the terrorists.

The report said: 'Ill-conceived immigration policies have made it easier for them to strike. European leaders were either naïve about the risks or failed to communicate honestly with the public the impact that accepting such large amounts of people would have on security.

'The fall-out from the decision to take in such a large amount of unvetted people in such a short time will continue for decades to come.'

The study found that there were 194 Islamist terror plots between January 2014 and December 2017. The total casualties were 357 deaths and 1,678 injuries.

Of those, 32 involved asylum seekers or refugees. They included the attack by IS-inspired gunman and suicide bombers who murdered 129 innocent people in Paris in November 2015 and Tunisian-born Anas Amri who killed 12 when he drove a truck into a Christmas market in Berlin in 2016.

Three plots took place in Britain. Sudanese asylum seeker Munir Mohammed, 36, was jailed for life with a minimum of 14 years in February this year after seducing a chemist he met through a Muslim dating website into helping him plot a bombing campaign.

Iraqi refugee Ahmed Hassan, 18, was jailed for life in March after he detonated a bomb containing on the London Underground at Parson Green in September 2017, an attack which injured 51. He told Home Office officials that he had been trained to kill by IS but was still allowed to stay in the country.

The third case involves a chip shop terror suspect behind an alleged Islamist Christmas bomb plot which was foiled in December. Andy Sami Star, 31, who came to Britain from Iraqi Kurdistan, is awaiting trial.

Ahmed Hassan was jailed for life in March

IS had direct connections to the majority of plots, with Germany targeted most and Syrians more frequently involved than other nationalities. Nearly three-quarters of plotters carry out, or have their plans stopped, within two years of arriving in Europe.

Most refugee and asylum-seeker plotters were radicalised prior to their entry to Europe. However, brainwashing occurring after arrival in Europe – often via propaganda videos on the internet - has become increasingly commonplace since late 2016, said the report.

Mr Simcox said: 'Europe has faced a severe threat from Islamist terrorism for years. Yet Chancellor Merkel's decision to open Germany's borders in 2015 unfortunately increased that threat.

'While only a minority of asylum seekers pose a security risk, the plots carried out by those exploiting migrant routes – in Paris, London, Berlin, Stockholm and elsewhere across Europe – demonstrate that even a low number of extremists can still cause huge amounts of damage.'

The report called on European leaders to tackle the threat by reducing the number of refugees from war zones scarred by Islamist conflicts, prioritise monitoring of high-risk recent arrivals and review intelligence used by the security services.

In 2016, Rob Wainwright, then director of Europol, the EU crime-fighting agency, revealed that increasing numbers of jihadists were using fake documents to sneak into Europe and some were posing as refugees.