By the Associated Press  LONDON — Britain’s political leaders sparred Sunday over who is responsible for the early release of a convicted extremist who launched a stabbing attack in central London that left two dead and injured three. Buses and cars remain on London Bridge in London, Sunday Dec. 1, 2019, after it being closed to traffic and public after an attack on Friday. Authorities in Britain say the convicted terrorist who stabbed to death two people and wounded three others in a knife attack Friday had been let out of prison in an automatic release program. (AP Photo/Alberto Pezzali / MANILA BULLETIN) The argument centers over the early release from prison of Usman Khan, who served roughly half his sentence before being set free. He was able to stab five people before being shot dead by police despite conditions imposed on his release that were supposed to protect public safety. After a one-day pause out of respect for victims, the Friday attack is dominating the political scene as the Dec. 12 election nears, shifting the focus, at least for the moment, from Brexit and the National Health Service to issues of security and criminal justice. Prime Minister Boris Johnson on Sunday blamed Khan’s freedom on changes in sentencing rules made by the last Labour Party government before Johnson’s Conservatives took power in 2010. He promised to toughen sentencing laws. “I think it is repulsive that individuals as dangerous as this man should be allowed out after serving only eight years and that's why we are going to change the law,” he told BBC’s Andrew Marr Show. Marr repeatedly challenged the prime minister by pointing out that the Conservatives had been in power for nearly a decade and not taken any steps to change the situation Johnson was complaining about. The accuracy of Johnson’s claim was challenged by Ed Davey, deputy leader of the Liberal Democrats, who told Sky News that the prime minister was misleading the public about the current law regarding early release of prisoners. "Either he's incompetent and doesn't know the law, or he's deliberately misleading people when we've got a tragedy on our hands, and I'm afraid, either way, it does not look good for the Prime Minister,” Davey said. Other rivals complained that Johnson was trying to score political points in the aftermath of the extremist attack. Labour leader Jeremy Corbyn accused the Conservatives of trying to provide security “on the cheap” and said he does not necessarily agree that all terrorist prisoners should be required to serve their full terms. He said it depends on the circumstances and called for the Parole Board and the probation service to be more actively involved.