LONDON - British Prime Minister David Cameron, defending his integrity in an emergency debate in parliament on Wednesday, said he regretted the uproar caused by his hiring of a former newspaper editor at the heart of a phone-hacking scandal.Under pressure from opponents to apologize, he said Andy Coulson, his former spokesman who once edited Rupert Murdoch's News of the World, had denied knowing of phone-hacking by the paper. But should Coulson turn out to have lied, the prime minister said he would then offer an apology.Cameron, who cut short a tour of Africa as parliament delayed its summer recess to quiz him, said in his opening statement: "I have an old-fashioned view about innocent until proven guilty. But if it turns out I have been lied to, that would be a moment for a profound apology. And, in that event, I can tell you I will not fall short."Cameron said, with a note of regret: "On the decision to hire him ... it was my decision ... Of course I regret and I am extremely sorry about the furore it has caused. With 20:20 hindsight ... I would not have offered him the job."