LONDON (AP) — Britain’s political leaders are sparring over who is responsible for the early release of a convicted extremist who launched a stabbing attack in central London that left two dead.

The argument centers over the early release from prison of Usman Khan, who served roughly half his sentence before being set free.

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.

Labour leader Jeremy Corbyn accused the Conservatives of trying to provide security “on the cheap.”

After a one-day pause out of respect for victims, the Friday attack is dominating the political scene as the election nears. The vote is set for Dec. 12.