Soldiers being sent to fight in Afghanistan have been described as "human shields for political reputation", by a longstanding critic of the conflict.
The Labour MP for Newport West, Paul Flynn, urged full withdrawal of combat troops, describing the situation as an "unwinnable war".
He said the planned withdrawal of UK combat troops in 2014 was merely for "political expediency".
He attacked the military operation, saying that promises on tackling drugs and corruption in Afghanistan had "failed hopelessly", warning that the country was likely to return to being a divided society.
A total of 437 UK military personnel have been killed since 2001, the majority in Helmand province, and Defence Minister Andrew Robathan paid tribute to the victims.
However, he criticised the approach of Mr Flynn, arguing that the UK was not going to "cut and run".
"We are in Afghanistan for one overriding reason - to protect our security," he concluded.