Prime Minister Gordon Brown Monday hailed the "sacrifice" made by British troops in Afghanistan as the death toll in the conflict reached 100, reported dpa.
His tribute was echoed by both the main opposition parties, the Conservatives and the Liberals, who also stressed that British soldiers were dying to "bring democracy" to Afghanistan.
Defence Secretary Des Browne said he remained convinced that Britain's involvement in Afghanistan was for a "noble cause."
But Anthony Philippson, the father of a British soldier killed in Afghanistan two years ago, said the conflict would turn into "as big a disaster as Iraq."
"When my son was killed, we thought it was just a bad accident, but week by week it's just got worse and I don't see an end in sight," he said.
The milestone figure of 100 British troop fatalities was confirmed Sunday as three soldiers of the elite Parachute Regiment fell victim to a suicide attack in Helmand province.
The deaths have reignited the debate in Britain about the mission in Afghanistan.
Although the total death toll is counted from the start of the conflict in 2001, the vast majority of the fatalities have occurred in the last two years.
"I want to pay tribute to the courage of all the 100 British troops who have given their lives in Afghanistan in the service of their country," the prime minister said in a statement.
"The risks they bear and the sacrifices they make should be in our thoughts, not just today but every day. They have paid the ultimate price, but they have achieved something of lasting value - helping turn a lawless region sheltering terrorists into an emerging democracy."
"They have paid the ultimate price, but they have achieved something of lasting value," said Brown.
Defence Secretary Des Browne said that while nothing could compensate for any individual loss, he remained convinced the campaign in Afghanistan was "the noble cause of the 21st century".
Browne said the insurgency could not be defeated by military means alone, and that governance, economic development and a "battle for the people" were equally important.
Conservative party leader David Cameron said the country owed "so much" to the servicemen and women fighting in Afghanistan, with the death toll serving as a "tragic reminder of how brave and courageous they are."
Liberal Democrat leader Nick Clegg also gave his party's explicit backing to the cause - in contrast to the Liberals' outspoken opposition to British involvement in Iraq.
"The consequences of failure in Afghanistan would be unimaginable - a boost to terrorists who seek to harm our way of life, an increase in hard drugs on our streets and terrible instability in an already unstable region," said Clegg.