The smart-missile cited as a major reason for Britain joining the bombing campaign in Syria has killed zero Isis militants there, it has been revealed.

A freedom of information request by the Huffington Post UK website found the Brimstone missile has not yet recorded any casualties in Syria since bombing started.

Only Britain and Saudi Arabia have access to Brimstone missiles and the Government argued that the weapon would represent a unique contribution by the RAF to fighting Isis.

Conservative minister David Jones described the weapons as “unique” while MP Sir Gerland Howarth said they represented a “key difference between us and other coalition partners”.

David Cameron himself said Brimstone missiles were among "some of the most accurate weapons known to man" and noted that the United States did not have access to them.

Brimstone missiles have a “fire and forget” capability and it has been claimed their introduction would help reduce civilian casualties and hit targets other weapons could not.

Brimstone missile strikes Isis building

Ministry of Defence figures however show only seven Isis casualties since the RAF joined in last year – five from US-made Hellfire missiles and two from the Paveway IV laser-guided bombs.

The missiles were not even used once in the first month of operations, with their first recorded deployment on 10 January against supply trucks in Raqqa.

British jets prepare for air strikes in Syria Show all 10 1 /10 British jets prepare for air strikes in Syria British jets prepare for air strikes in Syria A Tornado jet takes off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria British jets prepare for air strikes in Syria Pilots and ground crew prepare combat aircraft Panavia Tornados at RAF Marham at RAF Marham, UK Getty British jets prepare for air strikes in Syria A Eurofighter Typhoon jet takes off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria British jets prepare for air strikes in Syria A RAF Tornado arrives at RAF Akrotiri to begin operations in Akrotiri British jets prepare for air strikes in Syria A Tornado jet ahead of taking off from RAF Lossiemouth in Scotland, as RAF Tornado jets carried out the first British bombing runs over Syria, the Ministry of Defence has confirmed. The air strikes were carried out within hours of a vote by MPs in the Commons to back extending operations against Isis from neighbouring Iraq British jets prepare for air strikes in Syria Personnel work on a British Tornado after it returned from a mission at RAF Akrotiri in southern Cyprus British jets prepare for air strikes in Syria Two RAF Tornado GR4's, both with remaining weapons ordnance, approach RAF Akrotiri in Cyprus, as they return to the base after carrying out some of the first British bombing runs over Syria British jets prepare for air strikes in Syria A RAF Tornado takes off from RAF Akrotiri, on the Mediterranean island nation of Cyprus British jets prepare for air strikes in Syria A Tornado jet leaving RAF Lossiemouth in Scotland British jets prepare for air strikes in Syria AKA RAF Tornado arrives at RAF Akrotiri to begin operations in Akrotiri, Cyprus. The RAF has sent two further Tornado aircraft and six Typhoons to bolster aircraft now flying sorties to both Iraq and Syria

Brimstone has in total been used in nine raids since the vote and the end of last month.

Each missile costs around £100,000. They are used to attack ground targets and use radar homing and laser guidance technology; the weapons can destroy targets from seven miles away.

The RAF has deployed around half a dozen war planes in Syria to join US and other coalition jets fighting there.

The Ministry of Defence said in its FOI response: “Since December 2015 UK military air activity has contributed to the Coalition’s aim of disrupting and degrading Daesh military infrastructure, logistics and revenue streams inside Syria.

“This includes targeting oil infrastructure and enabling equipment under Daesh control, helping to reduce their ability to profit from selling oil to fund their activities.

“We have also targeted Daesh’s military equipment and infrastructure, including vehicles, defensive fighting positions firing on friendly forces, a tunnel complex, weapons stores and a command and control centre.