SUICIDE bomber Salman Abedi was among a clutch of terrorist suspects who were cleared to travel to and from Libya, “no questions asked”, when Theresa May was Home Secretary, it is claimed.

These exiles and British-Libyan citizens – including members of a proscribed Islamic terrorist organisation linked to al-Qaeda – were able to join the 2011 uprising against the Gaddafi regime, even though some were subject to counter-terrorism control orders, effectively house arrest.

It is alleged that these orders were lifted, passports were returned and the security service MI5 colluded in allowing them to go to Libya to fight.

Theresa May was Home Secretary at the time –from 2010 until she became Prime Minister last year.

Several foreign fighters now back in the UK have told the respected online news website Middle East Eye (MEE) that they went back and forth to Libya without hindrance while the fighting was going on.

Opponents of Colonel Gaddafi – such as Abedi’s Libyan parents – were given refuge in Manchester before the dictator was overthrown in 2011. Like them, their son went to Libya as the revolution against gathered momentum, and returned there on several subsequent occasions.

Sources spoken to by MEE suggest that the UK government facilitated the travel of Libyan exiles and British-Libyan residents and citizens keen to fight against Gaddafi, including those it was deemed posed a potential security threat.

One British citizen with a Libyan background said he was “shocked” that he was able to travel to Libya in 2011 shortly after his control order was lifted. “I was allowed to go, no questions asked,” said the source, who wished to remain anonymous.

Members of the Libyan Islamic Fighting Group, who were opposed to Gaddafi’s regime, had their British passports returned to them as the conflict in Libya escalated in 2011 – even though LIFG was proscribed as a terrorist organisation in 2005 by the British Government, describing it as “part of the wider Islamist extremist movement inspired by al-Qaeda”.

Belal Younis, a British citizen ,was stopped under ‘Schedule 7’ counter-terrorism powers on his return to the UK after a visit to the Libya in early 2011 and asked by an intelligence officer from MI5 if he was “willing to go into battle?”

Later, while travelling back to Libya, Younis was again stopped by two counter-terrorism officers but was given clearance to pass when he handed them the telephone number of the MI5 officer – who called him back before he boarded the plane to tell him he had “sorted it out.”

Counter-terrorism expert Charles Bird, who worked for the Ministry of Defence before taking up a position at the Centre for the Study of Terrorism and Political Violence at St Andrews University, said Libya’s porous borders still pose a problem to British security services.

“Manchester has been a centre for Libyan dissidents in the past few years," he said. "Those who were opposed to Gaddafi who were more militant and were given asylum in UK came to live in Manchester.

“Since the UK intervention in Libya which led to the overthrow of Gaddafi, Libya hasn’t really had a stable government. There are militias operating in various parts of the country. It’s basically got open borders so there are also extremists crossing the border from Mali, coming up through Niger. Once in Libya it’s not too difficult to cross to Europe" he said.

“Now that Islamic State is being gradually defeated in Syria and Iraq, the other concern is that they are moving their fighters into Libya where they already have an established base. It’s quite possible for someone of Libyan origin to go there and meet IS members who are Libyan, Syrian, Iraqi or other foreign fighters who have relocated to Libya.”

The official threat level for the UK was placed at the highest level, critical, for the first time in almost a decade after Abedi detonated an improvised explosive device at Manchester Arena, killing 22 people. Last night, the assessment was lowered to the second-most serious level, severe, which means an attack is considered highly likely.

Operation Temperer, a counter-terrorism plan activated the night after the attack, saw around 1,000 military personnel drafted in to boost the security response and help guard key sites that would normally have been filled by police firearms officers.

Yesterday armed officers were seen at major UK sporting and music events including the Scottish Cup Final at Hampden Park in Glasgow.