British Prime Minister Gordon Brown has warned Afghanistan’s President Hamid Karzai that he will not put the lives of British soldiers in harms way for a government that does not stand up to corruption.In a speech in London, Brown vowed not to walk away from Afghanistan as he seeks to bolster dwindling public support for the military mission. “It is not easy, the choices are not simple. There is no strategy that is without danger and risk but that is the responsibility of leadership, of government and of our armed forces – to do what is necessary, however difficult, to keep the British people safe. We cannot, must not and will not walk away,” Brown said. A recent poll shows more than a third of the British public want an immediate withdrawal of UK forces. Almost 40 percent want a quick exit from Afghanistan, while only a fifth believe they should remain. The same poll also showed nearly two thirds of those questioned thought victory was not possible, compared to 33 percent who believed the mission could still succeed. The sharp shift against the war comes after a spate of British troops’ deaths this week, including five soldiers killed on Tuesday by an Afghan police trainee.