After a bloody day of fighting which saw eight British soldiers die in the space of 24 hours, Foreign Secretary David Miliband said today that they were engaged in a battle for "the future of Britain".
He warned that Britain would not be secure until it had built security in Afghanistan.
He said that it was essential to prevent Afghanistan again becoming an "incubator for terrorism" and a launch pad for attacks on the UK and the West.
The Foreign Secretary insisted that ensuring that British troops had the protection they needed was the Government's "highest priority".
However Tory leader David Cameron said that it was a "scandal" that the forces still lacked the helicopters they needed to move around Helmand province.
Yesterday's deaths took the toll for this month so far to 15 and the overall total on operations in Afghanistan since 2001 to 184 - surpassing the 179 who died in Iraq.
Mr Miliband said that it had been a "grievous few days" for the families of those who had been killed, for the Army, and for the whole country.
"We know that they are engaged in a very, very difficult mission and we have a responsibility to engage the country in understanding that mission and supporting it," he told the BBC Radio 4 Today programme.
"This is about the future of Britain because we know that the badlands of Afghanistan and Pakistan - that border area - have been used to launch terrible attacks, not just on the United States, but on Britain as well.
"We know that until we can ensure there is a modicum of stability and security provided by Afghan forces for their own people, we are not going to be able to be secure in our own country."
Also this morning the head of Britain's armed forces insisted that the Taliban was "losing" the fight in Afghanistan.
Chief of Defence Staff Sir Jock Stirrup sent his condolences to the bereaved families, but said it was important to "remember why our people are fighting in Afghanistan and what they are achieving through their sacrifice and their courage".
In a televised statement, he went on: "It's tough going because the Taliban have rightly identified Helmand as their vital ground. If they lose there then they lose everywhere and they are throwing everything they have into it.
"But they are losing and our commanders on the ground are very clear of that. But it's going to take time and alas it does involve casualties, but when it's complete there will be the opportunity for considerably greater governance for the people of Helmand."
The top US commander in the Middle East has warned of tough months ahead in the fight against the Taliban.
General David Petraeus, head of the US Central Command, described the battle in the south of the country as "the longest campaign".
Meanwhile, a former head of the Armed Forces yesterday accused the Government of putting UK forces at risk and spending the "minimum they could get away with" on defence.
General Lord Guthrie, chief of the defence staff from 1997 to 2001, said commanders on the ground were struggling with too few troops.
He told the Daily Mail: "I spoke to an officer the other day who said that the Treasury had affected the operational safety of our soldiers, by preventing an uplift in our numbers."
It is "very likely" that fewer soldiers would have been killed by roadside bombs in Afghanistan if ministers had provided funding for more helicopters, he added.
Prime Minister Gordon Brown acknowledged it was a "very hard summer" for the troops but insisted the Government's resolution to seeing through the mission was "undiminished".
Speaking from the G8 Summit at L'Aquila in Italy, he said: "Our resolution to complete the work that we have started in Afghanistan and Pakistan is undiminished.
"We knew from the start that defeating the insurgency in Helmand would be a hard and dangerous job but it is vital."
The worst single loss of life in Afghanistan came in September 2006 when 14 people died in a Nimrod plane crash.Reuse content