British Prime Minister Gordon Brown today joined other world leaders in warning Afghan President Hamid Karzai to tackle corruption and improve governance, failing which international support will be withdrawn. Mr Brown said in a speech in London that he is not prepared to put the lives of British men and women at risk for a government that does not stand up against corruption. He was speaking after the killing of five British soldiers by an Afghan policeman in southern Helmand early this week. US President Mr. Barack Obama and UN mission chief in Afghanistan have already warned the new government to address corruption and deliver services to the people. <br/>