A serving soldier today accused the government of abusing the trust of the army and serving soldiers by continuing military action in Afghanistan.

Lance Corporal Joe Glenton, who is facing a court martial for refusing to return to Afghanistan, made his comments before an anti-war demonstration in central London.

Glenton, 27, led former colleagues, military families and anti-war protesters in the march, calling for British troops to be brought home.

He told protesters at Speakers Corner in Hyde Park that he found it distressing to disobey orders but felt that he had been left with no choice.

The centre of London was brought to a temporary standstill as thousands of protesters made their way to Trafalgar Square.

Some of the crowds chanted "Gordon Brown, terrorist" while others sang "What do we want, troops out".

His statement, released before the rally, read: "It is distressing to disobey orders but when Britain follows America in continuing to wage war against one of the world's poorest countries I feel I have no choice.

"The Geneva Convention was launched after the Second World War and the Nazi extermination of six million Jews. It means no soldier can say I was just obeying orders.

"Politicians have abused the trust of the army and the soldiers who serve. That is why I am compelled and proud to march for Stop The War Coalition today."

Peter Brierley, whose son Lance Corporal Shaun Brierley was killed in Iraq in 2003, also attended the march.

Brierley, a 59-year-old CCTV supervisor from Batley, West Yorkshire, recently hit the headlines after refusing to shake hands with the former prime minister, Tony Blair, accusing him of having blood on his hands because of the Iraq war.

Brierley said British troops needed to be withdrawn from Afghanistan as soon as possible.

"They are not doing any good while they are over there," he said. "They need to leave the country to sort itself out. While the British troops are there they are actually bringing in insurgents who are coming in to fight."

The protest came as a poll found that almost half of the UK public believe that military victory in Afghanistan is impossible and many believe that British troops should be brought home either immediately or within the next year.

The YouGov survey for Channel 4 News found just 6% of the 2,042 people polled on October 22 and 23 believed British troops were winning the war, 36% said eventual victory was possible and 48% who said victory was not possible.

A quarter said British troops should be withdrawn "immediately" and 37% said most should be withdrawn soon, with the remainder pulling out within a year or so.