Security experts have warned that the threat to the UK's border stretches across the South

France has more than 40 vessels available to tackle the same threat but Britain has five - only three of which are currently operating in UK waters.

The dire shortage of Border Force craft has fuelled fears that the south coast, including parts of Hampshire, are "wide open" to people smugglers.

Security experts have warned that the growing threat to Britain's shores stretches from Dover to Portsmouth and possibly beyond.

With desperate migrants willing to pay gangs at least £8,000 each to attempt the Channel crossing the problem seems set to escalate.

The issue of people entering European countries illegally by boat is no longer confined to far off shores. 

Last month 17 Albanians were found on a catamaran in Chichester Harbour and 18 of their fellow countrymen were rescued off the Kent coast.

The two incidents have raised fears that migrants could soon be coming ashore in Hampshire - one of the UK's biggest sailing centres.

With so many coves, inlets and quiet waterways along our coast and the lack of patrol boats operating in the Channel waters some believe Hampshire could be ideal for people smugglers to ply their trade.

Mike Cooper, commodore of a sailing club based at Ashlett Creek, near Fawley, said: "This part of the south coast is some distance from France but it could happen. 

"Somewhere like Ashlett Creek would be a nice backwater in which to offload people."

New Forest councillor Michael White is a member of the Royal Lymington Yacht Club and a former mayor of the town.

He said: "I don't think people-smuggling is likely to occur in Lymington - all the marinas are very well covered by CCTV.

"But it might be possible to smuggle migrants into somewhere like Keyhaven, which is very quiet at night."

Lymington Yacht Haven and other sailing facilities along the Hampshire coast are already on their guard. 

A spokesman for Yacht Havens Group Ltd said: "We're in regular communication with Border Force and the Hampshire Police Marine Unit to source the best advice.

"All our marinas take security very seriously, with secure-access bridgeheads on to the pontoons, CCTV, 24-hour staff and daily pontoon walks to check on boats.

"A fortnight ago we hosted a marina manager conference which included a special presentation from the marine unit. We discussed maritime security at length, with the unit offering advice on what to watch for.”

The security of Hampshire's coastline is one of the issues confronting Michael Lane, the county's new Police and Crime Commissioner.

Mr Lane told the Daily Echo: “Protecting our borders, particularly vulnerable points such as ports and marinas, is crucial and an essential policing and national security role.

"Our marine unit and frontline policing are extremely valuable in this task.

“Partnership with other bodies which share this responsibility and are in charge of reviewing the risks were a focus during my recent campaign to be elected.

"As part of this I met with senior government officials to raise and discuss the necessity of joined up working to keep residents safe and to protect our borders.”

But the Immigration Services Union, which represents Border Force staff, has warned that large stretches of the coastline are being left unguarded.

A Border Force insider is reported to have said: "According to the Director General we are the best border force in the world. What a joke."

Concern has increased following the revelation that a proposed new fleet of patrol craft will not be fully operational until the end of 2017.

That will be almost two years since the Chief Inspector of Borders, David Holt, warned that small ports, remote beaches and secluded coves were an easy target for people smugglers. 

But illegal immigration is not the only problem posed by Britain's 7,700-mile coastline.

Serious safety concerns were raised after Islamic State terrorists used the Mediterranean crisis last year to enter Europe posing as refugees or economic migrants before unleashing their deadly attacks on Paris and Brussels.

Martyn Underhill, Dorset's Police and Crime Commissioner, has warned the government that lax security could result in a similar outrage in Britain.

In a hard-hitting letter to Home Secretary Theresa May earlier this year Mr Underhill said: "We need an urgent review of staffing strategy and funding before we suffer a catastrophic attack.

"Border Force whistleblowers tell us the system is failing in maritime ports."

His letter added: "To ignore the obvious failings in the Border Force may lead to our citizens suffering an attack that neither your government, nor your personal career, will survive."

The Southampton-based Maritime & Coastguard Agency has vowed to take the necessary action if its suspicions are aroused during a rescue mission.

A spokesman said: "We would of course record as much information as possible and pass it on to the relevant agency, whether it be migrant related or general crime, and where possible co-ordinate our response in conjunction with any advice given by them."

New maritime powers introduced in the past few days aim to crack down on illegal immigration.Border Force officers will be able to stop, board and detain vessels and arrest anyone suspected of breaking immigration laws in the UK waters.

The head of the EU's law enforcement agency has sought to calm fears expressed in the wake of recent incidents.

Rob Wainwright, director of Europol, said: "It is worth pointing out that because Britain is an island, because Britain is outside the Schengen zone, but also because it has information-sharing arrangements with the EU partners, it still has one of the strongest borders in Europe."

Harbour bosses in Hamble and other parts of the county declined to comment.

But a spokesman for the River Hamble Harbour Authority said: “We have no evidence of people smuggling or migration via the River Hamble.

"We keep our eyes open and liaise very closely with agencies responsible for borders and security, including routine meetings with Border Force.”