The Falklands will be left at the mercy of Argentina because of a delay in deploying a shield similar to Israel’s Iron Dome system, Defence sources have warned.

The Telegraph understands that Sky Sabre, a medium- and short-range surface-to-air missile, which uses the technology behind Israel’s Iron Dome shield, has still not become fully operational, despite a deadline of 2020.

Now deploying troops are having to train on the old Rapier, a short-range air defence system introduced in the late 1990s, which sources have described as being “bordering on unserviceable”.

It is not clear what has caused the delay to Rapier’s successor. However, troops are said to be concerned that the old system will leave the overseas British territory vulnerable to attack from Argentinian forces.

Last year, The Telegraph revealed that Spain had embarked on a secret lobbying drive to push US congressmen into supporting a plan to strip Britain of sole sovereignty over Gibraltar months after the Brexit vote.

Meanwhile, Argentina renewed its campaign to lay claim to the islands over the past year, appointing a minister for them and lobbying at the United Nations.

Alberto Fernandez, Argentina's president, on the Day of the Assertion of the Argentinian Rights over the Malvinas, when Argentina annually lays claim to the disputed islands

Justin Bronk, a research fellow of airpower and technology at the Royal United Services Institute (RUSI) warned Rapier was “obsolete” and the “threat landscape within which Rapier was designed for bears little resemblance to the threat landscape today”. 

Mr Bronk cautioned that due to the fact that each of Rapier’s launcher can only guide one missile at a time, it would not be able to defend itself against “multiple incoming threats”, unlike Sky Sabre, which can “guide large numbers of missiles in the air simultaneously against lots of incoming threats, so it’s much harder to swamp”.

He added that Sky Sabre’s ability to have 360 degree coverage against multiple incoming threats at once meant it could face off today’s threats, such as modern loitering munitions, missiles and unmanned aerial vehicles.

He said in such a situation Rapier, which is broadly an anti-aircraft and anti-helicopter missile, “would become very quickly overwhelmed, whereas, at least in theory, Sky Sabre is designed to handle saturation type attacks”. 

Mr Bronk added: “Rapier is totally obsolete in the modern battlefield”.

While he cautioned that he did not believe there was a serious threat of the Argentinians taking over the Falklands, the delay to Sky Sabre he criticised another “missed deadline” by the Ministry of Defence.

Earlier this week, The Telegraph revealed that the new fleet of Ajax tanks bought by the Army for £3.5 billion cannot be driven safely over 20mph and is four years behind schedule to be deployed.

In numbers | The residents of the Falkland Islands

Mr Bronk added that the delay to Sky Sabre was “another example as we’ve seen very, very prominently over the last couple of days with Ajax, of the Army’s procurement process and not meeting its own deadlines”.

Tobias Ellwood, chairman of the Defence Select Committee, said: “The Rapier surface to air missile has served the Army well, but this 1970s technology is now obsolete.

“If you cannot control the skies – then your land forces are sitting ducks. All the more so with ever wider utility of drones by both state and non-state actors.”

Mr Ellwood warned that if the UK failed to upgrade its defence systems then it “cannot protect our troops in our theatres of operations and static targets in the UK”. 

“We cannot afford to allow the introduction of Sky Sabre to slip,” he said. 

An MoD spokesperson said:“The deployment of Sky Sabre experienced a delay due to the Covid-19 pandemic, which has resulted in the Rapier System being extended for use.

“The Rapier System remains fully operational whilst in service and holds a central role within Ground Based Air Defence in the Falkland Islands.”