The Ministry of Defence (MoD) has said its armoured vehicles are "dealing with the demanding conditions in Iraq" - after reports said light patrol Foxhounds have broken down in the heat.
The vehicles, first deployed in Afghanistan in 2012, were described as providing "unparalleled protection for its weight and class".
The MoD spent more than £370 million on the 400 Foxhounds which were brought in to replace the Snatch Land Rover.
Last month, the Defence Secretary Sir Michael Fallon apologised to the families of the 37 British soldiers killed while travelling in lightly armoured Snatch Land Rovers.
He wrote to families apologising for delays in bringing in alternative protected vehicles "which could have saved lives".
However, the BBC has quoted an unnamed Army sergeant as saying the replacement vehicles have reliability issues in the heat.
A MoD spokeswoman said:
"Foxhound has dealt with the demanding conditions in Iraq, kept our soldiers safe and is delivering the required operational output in the defeat of Daesh.
"The Urgent Operational Requirement Programme has saved countless lives in operations in Iraq and Afghanistan.
"Decisions on which equipment to continue to support and which to sell are made with current and future operational requirements in mind."