Britain lost more soldiers in Afghanistan in 2008 than in any year since international forces intervened to oust the Taliban regime in 2001.

The last man to die was a Royal Marine from Arbroath-based 45 Commando, killed in an explosion while he patrolled the Sangin valley on New Year's Eve.

He is the 12th Royal Marine to die in action in the past two months and the 29th since 2006, two more than were lost in the Falklands War in 1982.

A total of 51 UK soldiers died over the past 12 months - mainly as a result of roadside bombs - compared with 42 in 2007 and 39 in 2006.

The past year was also the worst for US forces, with 155 men killed, and the second worst for the Canadians with 32 dead. Ottawa's forces lost 30 men in 2007 compared with 36 in 2006 as they battled the Taliban for control of their heartland around the southern city of Kandahar.

The Danes, fighting with British forces in Helmand, lost 12 men in 2008, double the number killed in 2007.

The French, often criticised for keeping their troops clear of the most dangerous areas, suffered 11 dead. Ten paratroopers were killed in August in a Taliban ambush 40 miles east of Kabul, the capital.

The mounting death-toll of allied forces is one of the main reason why the US is preparing to "surge" 30,000 soldiers into Afghanistan to regain the initiative from the insurgents.

A military source told The Herald: "The Taliban are adaptable. Although they still mount conventional operations against us and engage us in open firefights when they think they have the advantage, they have switched their main effort to suicide bombers and booby-traps.

"They lost upwards of 8000 fighters in 2006-07 when they came up against Nato's superior firepower and air strikes.

"That taught them the folly of trying to take us on man-for-man at every opportunity. Now they pick the times and places and use their own strategic firepower - roadside explosive devices and suicide vests - to inflict losses."

Britain has had 526 soldiers wounded in action and the Canadians 360 since 2006.

Between them, they have sustained battlefield casualties in dead and injured equivalent to two front-line battalions.

The UK has lost 17 soldiers and Royal Marines killed and around 60 wounded in action fighting the Taliban in central Helmand in the past eight weeks alone. More than 200 injured and sick troops have been airlifted out of Afghanistan since October.

The number of injured troops being evacuated from Helmand is now more than double that of last year. In November 2007, 33 injured troops were flown out. The figure was 79 this November. Defence sources describe improvised explosive devices (IEDs) as the "main killer" of British troops in Helmand. Since October, 11 soldiers and Marines have been killed by IEDs while four have been shot dead and two were killed in a rocket-propelled grenade attack. Of Britain's 526 battlefield wounded, 153 are classed as "very seriously" or "seriously" injured.

While the MoD insists that the numbers of British soldiers suffering from post-traumatic stress disorder (PTSD) remains relatively low, the Canadians report that 395 of their men have been diagnosed with the debilitating psychiatric illness after service in Kandahar.

One Canadian source said: "We don't have the necessary statistical evidence to hand as yet, but the high incidence of PTSD among the 2500-strong garrison we maintain in Afghanistan could be the result of a higher number of reservists among those serving on the front line.

"While you Brits draw about 8% of your garrison from the Territorial Army, we deploy a steady 20% of our manpower from the reservist pool."

The UK has suffered 137 dead in Afghanistan, the Canadians 106 and the Americans 630, all but a handful since the main campaign to stabilise the country was launched in 2006.