The risk to the soldiers is increased if they have to get out of the car, the UK Times newspaper reported, citing Major Andy Brown of the Royal Electrical and Mechanical Engineers.
"That’s why we wear personal protective equipment. It’s not a gamble, it’s a calculated risk. Like any piece of kit, there have to compromise," the officer was quoted as saying.
According to Brown, the car issues had not impacted the operations. However, another source, an infantry sergeant, told the newspaper that the troops had had "quite a few problems with them."
Brigadier Simon Humphrey, commander of British forces in Afghanistan, called the vehicles reliable and stressed he had never had any issues with them.
An army spokesman reportedly pointed out that the cars had "saved lives," but did not give details on how often they broke down when out on a mission.
The UK troops in Afghanistan contribute to an international anti-terrorist mission. Afghanistan has been plagued with instability and security threats for years.