People smugglers are “abusing” soft border controls between Ireland and the UK to get their human cargo past authorities, the National Crime Agency (NCA) has warned.

Officials told The Independent they were concerned about an increase in the number of gangs found to be working through the common travel area, which the government has said it wants to maintain after Brexit.

Passports are not currently required for British and Irish citizens travelling between the two countries, and although air and sea carriers say they require some form of identification, documents are not always checked.

In January, six Indian nationals were arrested as they attempted to board flights to the UK from Ireland using counterfeit passports supplied by a man in Dublin.

In another recent case, a gang stands accused of smuggling people from Georgia into Britain from Ireland, while a Vietnamese group was found to be trafficking workers into nail bars along the same route and several factories producing counterfeit documents have been seized.

House of Lords vote out proposal for 'checks and controls' at Irish border after Brexit

Tom Dowdall, deputy director of the NCA who leads on human trafficking, said organised crime groups are “changing their modus operandi”.

“People from eastern Europe and further afield are coming into the UK via the common travel area through the Republic of Ireland,” he said.

“Some are flying into Ireland and travelling into the UK by air or ferry, and we have also seen coaches going to Ireland.”

In several cases discovered so far, gangs have been giving migrants fake passports, with some instructed to destroy them mid-flight to cover their tracks.

Earlier this year the NCA led an international operation that saw 12 members of a gang arrested for providing false documents and cash from a factory in eastern Europe.

In the Georgia case, migrants were allegedly given forged identity papers that allowed them to work in Britain.

Officials are monitoring a wider flow of clandestine Georgian migrants since the European parliament voted to allow them to travel into the Schengen zone without visas last year.

“They would fly into Dublin and seek asylum in the knowledge that they would not be detained before any onward movement into the UK,” an NCA official said.

The agency says it is also aware of groups who exploit the common travel area by giving illegal migrants false evidence of a history of living in Ireland, and therefore allowing them to enter Britain.

“Certain nationalities are already coming into the UK inadequately documented,” Mr Dowdall said. “They get on a plane with documents but come off without, they destroy them. Iranians are paying £20,000 to £30,000 to get to the UK. It’s a very expensive way of doing it.”

The National Crime Agency said some migrants fly to the UK from Ireland, while others take ferries (AFP/Getty)

Mr Dowdall said organised crime groups were moving people directly from source countries or attempting to disguise their routes.

“Quite often we see movements from the likes of Vietnam for example flying via Moscow, then into western Europe and on into the UK,” he added.

“These are not new routings but organised crime groups and use those that have perhaps become more fashionable for them, more easy or because they are able to eliminate barriers on those routes.

“There are examples of where they are able to corrupt either public officials or people involved in the transport industry along that routing.

“We will see things spring up very quickly and then we work to stem that with partners in host countries.”

Mr Dowdall said he could not yet estimate the number of immigrants illegally entering the UK via the common travel area, but stressed that the main route for clandestine arrival was still sea ports in southern England.

“You can simply get lost in the traffic that comes through the likes of Dover or the Channel Tunnel,” he added. “Although we see episodes of people coming to other ports and abuses of things like small vessels, rigid inflatable boats and yachts, these are not methods that would be used in significant volume.”

On Thursday an Albanian people smuggler was jailed for six years for trying to sail eight other Albanians into the UK in an inflatable boat.

Brexit threatens life on the Irish border: in pictures Show all 15 1 /15 Brexit threatens life on the Irish border: in pictures Brexit threatens life on the Irish border: in pictures An abandoned shop is seen in Mullan, Co Monaghan. The building was home to four families who left during the Troubles. The town was largely abandoned after the hard border was put in place during the conflict. Mullan has seen some regeneration in recent years, but faces an uncertain future with Brexit on the horizon Reuters Brexit threatens life on the Irish border: in pictures A defaced ‘Welcome to Northern Ireland’ sign stands on the border in Middletown, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Mervyn Johnson owns a garage in the border town of Pettigo, which straddles the counties of Donegal and Fermanagh. ‘I’ve been here since 1956, it was a bit of a problem for a few years. My premises has been blown up about six or seven times, we just kept building and starting again,’ Johnson said laughing. ‘We just got used to it [the hard border] really but now that it’s gone, we wouldn't like it back again’ Reuters Brexit threatens life on the Irish border: in pictures Farmer Gordon Crockett’s Coshquin farm straddles both Derry/Londonderry in the North and Donegal in the Republic. ‘At the minute there is no real problem, you can cross the border as free as you want. We could cross it six or eight times a day,’ said Crockett. ‘If there was any sort of obstruction it would slow down our work every day’ Reuters Brexit threatens life on the Irish border: in pictures John Murphy flies the European flag outside his home near the border village of Forkhill, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Potter Brenda McGinn stands outside her Mullan, Co Monaghan, studio – the former Jas Boylan shoe factory which was the main employer in the area until it shut down due to the Troubles. ‘When I came back, this would have been somewhere you would have driven through and have been quite sad. It was a decrepit looking village,’ said McGinn, whose Busy Bee Ceramics is one of a handful of enterprises restoring life to the community. ‘Now this is a revitalised, old hidden village’ Reuters Brexit threatens life on the Irish border: in pictures Union Flag colours painted on kerbstones and bus-stops along the border village of Newbuildings, Co Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures Grass reflected in Lattone Lough, which is split by the border between Cavan and Fermanagh, seen from near Ballinacor, Northern Ireland Reuters Brexit threatens life on the Irish border: in pictures Donegalman David McClintock sits in the Border Cafe in the village of Muff, which straddles Donegal and Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures An old Irish phone box stands alongside a bus stop in the border town of Glaslough, Co Monaghan Reuters Brexit threatens life on the Irish border: in pictures Billboards are viewed from inside a disused customs hut in Carrickcarnon, Co Down, on the border with Co Louth in the Republic Reuters Brexit threatens life on the Irish border: in pictures Seamus McQuaid takes packages that locals on the Irish side of the border have delivered to his business, McQuaid Auto-Parts, to save money on postal fees, near the Co Fermanagh village of Newtownbutler. ‘I live in the south but the business is in the North,’ said McQaid. "I wholesale into the Republic of Ireland so if there’s duty, I’ll have to set up a company 200 yards up the road to sell to my customers. I’ll have to bring the same product in through Dublin instead of Belfast’ Reuters Brexit threatens life on the Irish border: in pictures A disused Great Northern Railway line and station that was for customs and excise on the border town of Glenfarne, Co Leitrim Reuters Brexit threatens life on the Irish border: in pictures Alice Mullen, from Monaghan in the Republic of Ireland, does her shopping at a former customs post on the border in Middletown, Co Armagh. ‘I’d be very worried if it was a hard border, I remember when people were divided. I would be very afraid of the threat to the peace process, it was a dreadful time to live through. Even to go to mass on a Sunday, you’d have to go through checkpoints. It is terribly stressful,’ said Mullen. ‘All those barricades and boundaries were pulled down. I see it as a huge big exercise of trust and I do believe everyone breathed a sigh of relief’ Reuters Brexit threatens life on the Irish border: in pictures A bus stop and red post box stand in the border town of Jonesborough, Co Armagh Reuters

Afrim Xhekaliu, 41, made an emergency call in the early hours of 31 January as the rigid inflatable boat he was sailing got lost in the freezing English Channel after setting off from France.

The RNLI found him at the controls wearing a life jacket and wetsuit, while the seven other men and a woman on board were poorly dressed and suffering from hypothermia.

Smugglers’ preferred transit method of lorries can also be life-threatening, with 68 people found crammed into lorries in the Essex port of Harwich in 2015 and the bodies of 71 asylum seekers from Iraq, Syria and Afghanistan found decomposing in a lorry in Austria that same year.

Mr Dowdall said Belgium was a “prevalent” exchange point for people smugglers loading up vehicles to send onwards to the UK, dodging surveillance at service stations before driving onwards to Calais.

“Some of the drivers are being duped but an increasing number are complicit,” he added.

The NCA is working with French, Belgian and Dutch police to detect people smuggling across the English Channel and North Sea.

A Home Office spokesperson said the Garda National Immigration Bureau, Police Scotland and other authorities are tackling abuse of the common travel area with intelligence-led checks and enforcement operations.

“There is a high level of cooperation between the UK and Irish governments to disrupt organised crime groups and tackle organised immigration crime, modern slavery and human trafficking,” he said.