More than 10% of the training exercises scheduled for Britain's armed forces were cancelled last year, mainly to save money or because the troops involved were already serving on the frontline in Afghanistan or Iraq, The Herald can reveal.

Ministry of Defence figures also show that the cancellation rate has increased since 2006, despite official denials that the services are increasingly overstretched.

A total of 76 "training events" were either scrapped or UK contingents due to take part were withdrawn in 2007 out of the 727 national and multi-national exercises on the defence planning schedule. That amounts to 10.5%.

In 2005, 79 of 379 exercises - 20% - were abandoned. In 2006, 58 out of 533 were scrapped, amounting to more than 9% of the total.

Nick Harvey, the LibDem defence spokesman, yesterday accused the MoD and the government of neglecting the long-term effectiveness of the forces by pursuing policies which sacrificed vital training needs in the interests of expediency and cost-savings.

"Operational commitments in Iraq and Afghanistan are clearly having a big impact on our forces' ability to conduct military exercises. If these exercises are abandoned then we are in danger of undermining our wider operational capabilities," he said.

"It is further proof that our armed forces are critically overstretched and suffering from the demands made by fighting in two countries.

"The government must set a timetable for a full withdrawal of troops from Iraq and establish a new Strategic Defence Review to resolve the critical problems caused by overstretch."

General Sir Richard Dannatt, the head of the Army, said last year that, because of the focus on Iraq and Afghanistan, insufficient time and resources were being devoted to training.

A spokesman for the MoD said all troops were given specific "deployment training" before serving in Iraq or Afghanistan and there was no question of compromising that training.

He added: "Cancellations do not include training that is necessary for personnel to perform effectively on operations. It is our responsibility to deliver the requisite amount of training.

"While we are facing high operational tempo, we ensure that everyone deployed is fully prepared."

Of the training events cancelled last year, 29 were removed as "savings measures", another 18 for operational commitment reasons, and 20 for "changed priorities".

Seven due to take place abroad were cancelled by host nations.

A total of 33 air exercises were among those abandoned. It costs £33,000 an hour to crew, fly and maintain a Tornado GR4 strike aircraft, £30,000 for a Nimrod surveillance jet, £46,000 for Apache helicopter gunships and £24,000 for Chinook transports.

On the MoD's own figures, 12% of the army is on active operations and another 7% on "other military tasks", while 4% of the Royal Navy and 7% of the RAF are engaged on support operations.

As of this week, there were 13,280 service personnel deployed overseas, including 7000 in Afghanistan and 4200 in Iraq.

A similar number are recovering from operational tasks and another 13,000 preparing to go as replacements for those already there.