Cannibalisation of Britain's Apache attack helicopter squadrons for spare parts has trebled since 2003 because of the punishing tempo of operations in support of frontline troops in Afghanistan.

Figures released by the Ministry of Defence show that 251 parts were stripped out of other gunships in the 12 months up to January 31 this year to keep the eight machines used as flying artillery in Helmand province available for missions. This compares with 80 incidences in 2003 and 72 in 2004.

The MoD said: "All UK helicopters deployed to Iraq and Afghanistan are considered fit for purpose, but not all will be available for operational flying each day due to routine maintenance requirements.

"However, these factors are taken into consideration, and sufficient helicopters are provided to meet current operational requirements.

"Cannibalisation is an accepted short-term measure employed by aviation forces around the world to ensure the maximum number of aircraft are available. It is often the only course of action where replacement items cannot be sourced in the required time frame."

Major-General Ton van Loon of the Royal Netherlands Army, who was in charge of the coalition's southern command last year, added: "Without helicopters, operations in southern Afghanistan are not possible. It is unacceptable that a soldier dies because the medevac helicopter and its attack helicopter escort are not available. Several times last year, we came very close to not getting this right because we were stretched."

Lord Drayson, the UK's former procurement minister, denied last year that shortages put anyone's life at risk.

"There is no shortfall of spare parts for Apache helicopters in Afghanistan."

The MoD claims that commanders in Iraq and Afghanistan had enough helicopters to do "key tasks" although it admits that "with more they could do more".