LONDON, England (CNN) -- British Prime Minister Gordon Brown has defended the UK's involvement in the war in Afghanistan following the British Army's bloodiest day of the near eight-year conflict. Soldiers from the Welsh Guards carry the coffin of Maj Sean Birchall, killed on patrol in Afghanistan in June. Addressing lawmakers on Monday, Brown said the security of Afghanistan was crucial to preventing terrorist attacks elsewhere in the world. "In 2009 the case for our continued involvement is the same: to prevent terrorist attacks in Britain and across the world by dealing with the terrorist threat at its source -- that crucible of terror on the border and mountain areas of Afghanistan and Pakistan," Brown told the House of Commons.
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Gordon Brown: Afghanistan campaign crucial to preventing terror attacks
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Brown rejects charge UK troops killed because of lack of helicopters
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UK shocked by deaths of 15 troops in 10 days including 8 in one day
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UK forces have joined with U.S., Afghan troops in offensive in Helmand
"We urge the British government to end now this futile war which, if continued, will only mean more wasted lives of @placeholder soldiers, countless deaths of Afghan civilians and further devastation of a country that has suffered from decades of war and occupation," the group said in a statement.