MANCHESTER, England (AFP) - British premier Gordon Brown used a highly personal speech Tuesday to argue he was a serious leader for serious times in a crunch bid to silence rebels at his Labour Party's conference. Brown said "the way to deal with tough times is to face them down" on the last full day of the conference in Manchester, northwest England, dominated by talk of a leadership challenge and global economic turbulence. "I'm not going to try to be something I'm not," the prime minister said in a 53-minute-long speech, which stressed his experience and received a warm, five-minute standing ovation. "If people say I'm too serious, quite honestly there's a lot to be serious about " I'm serious about doing a serious job for the people of this country." He also repeatedly took aim at David Cameron, the youthful leader of the main opposition Conservatives who threaten to oust the centre-left Labour in the next general election, which must be held by mid-2010. "This is no time for a novice," Brown said, pledging to provide a "rock of stability and fairness" for the nation. In a highly unusual step highlighting his softer side, the 57-year-old bookish Scot was introduced by his wife Sarah, who said she was "proud" of the work her husband was doing. The British premier stressed he would do "all it takes" to bring stability to world financial markets. Speaking to AFP minutes after Brown 's speech, Foreign Secretary Miliband said it was "the best speech of the week and "excellent".