The Ministry of Defence is insisting that helicopters due to be deployed in Afghanistan will be "fit for operational use" as fears were raised that they were vulnerable to Taliban attack.
Six Merlin helicopters, which will allow commanders to move troops or kit around Helmand by air rather than road, will reportedly not be able to fly combat missions due to a lack of armour plating.
According to the Daily Telegraph, pilots are angry that requests for Kevlar armour, which would cost around £100,000 for each aircraft, have been ignored.
But a Ministry of Defence spokesman said Merlin Mk3 helicopters were fitted with ballistic protection as standard.
His comment came as Conservative leader David Cameron said there was a "very strong case" for sending more British troops to Afghanistan if they helped transfer more power to Afghan security forces.
Speaking on the BBC's Westminster Hour, Mr Cameron said: "If what the military are asking for is more troops in Afghanistan to speed up the training of the Afghan national army, it does seem to me there's a very strong case for saying yes to that.
"Because the faster we can build up the Afghan national army and the police, the faster we'll be able to 'Afghan-ise' the problem and the situation and the more rapidly we'll actually be able to end that mission and bring our troops back home."
The MoD spokesman refused to give details of the level of armour available to the helicopters in case it offered assistance to Taliban forces, but added that armour was just one of the elements involved in protection.
He said: "Our Merlin Mk3 helicopters have ballistic protection as standard, and are being fitted with a range of modifications to make them fit for operational use.
"For reasons of operational security, we do not discuss specific defensive capabilities of our aircraft. To do so would potentially offer enemy forces a tactical advantage.
"Nevertheless, we will continue to provide the greatest level of force protection for both crew and passengers while maintaining performance in Afghanistan's particularly arduous environment."
The political row over the provision of helicopters to commanders in Afghanistan erupted during a bloody July which saw a mounting death toll as troops engaged in Operation Panther's Claw.
The ability to transport troops by air reduces the risk of attack from improvised explosive devices (IEDs) which have claimed dozens of lives during the conflict.
During Panther's Claw alone, British forces came across a total of 153 IEDs.
The six Merlins are due to be deployed to Afghanistan at the end of this year.
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