Police fear terrorists using UK black market to buy weapons for Paris-style gun attack

It comes as the head of MI5 warns there are around 3,000 potentially violent extremists in the UK, and most of them are British

The National Crime Agency (NCA) and Scotland Yard's counter-terrorism command today launched a campaign urging the public to report any fears of criminals handling firearms (PA)

Police have revealed half of extremist terror plots foiled by British police in the past two years have involved a plan to buy guns, amid a surge in gun seizures in the UK.

The revelations have prompted fears that links between street gangs and terrorists could give extremists access to weapons and risk the type of mass shootings most recently seen in the Paris attacks.

At least 10 terrorist attacks have been foiled by British security services and police in the past two years, five of which have involved guns.

It comes as the head of MI5 issued a warning that there are about 3,000 potentially violent extremists in the UK, and most of them are British.

Andrew Parker, who has been director general of the UK security service for nine years, said in an interview with The Guardian published on Tuesday that there was a "large homegrown problem of potentially violent extremists in the UK," estimating there were "about 3,000 in number".

The spy chief said the number of potential extremists living in the UK was one of three aspects that make up the wider Islamic extremist threat - along with the members of Isis operating in Syria and Iraq and the isis's attempt to spread its "toxic ideology" online.

The interview was published hours after the National Crime Agency (NCA) and Scotland Yard's counter-terrorism command launched a joint campaign urging the public to report any fears of criminals handling firearms.

Assistant commissioner Mark Rowley, who is in charge of counter-terrorism for the police, said: “Half of the plots that have been disrupted in recent years have involved terrorist plotters who tried to get hold of guns.

“The links we see tend to be from terrorists into criminals in the communities they hail from. It will often be people involved in low-level organised crime or gang activity.

“Law enforcement, together with security and intelligence services, are working tirelessly to locate these weapons, confront the terrorist threat and keep the public safe.”

Director of the NCA, Lynne Owens, said disrupting the supply of firearms has “never been a more significant priority”.

Ms Owens said: “Currently we believe we hold an advantage. There is low availability of illegal firearms in the UK compared with European and international partners, but it is not an advantage that we take for granted, and to maintain that advantage we must not stand still.”

The NCA and police seized a total of 884 firearms last year, which were sent to the National Ballistics Intelligence Service for forensic analysis.

There are estimated to be about 750 organised crime gangs in the UK who are involved with guns.

An attack by gunmen is considered to be the most significant terrorist threat and a recent review of London's counter-terrorism arrangements suggested that UK border security should be stepped up to stem the flow of weapons into the country.

Since March there has been an increase in gun crime in London, with the Metropolitan Police recording 202 firearms discharges in July and August, compared with 87 in the same months last year.

The Home Office has meanwhile insisted the UK has “one of the most secure borders in the world”.