He told the House of Commons a statutory instrument introducing the change would be introduced in Parliament and both houses would be able to discuss the proposal before Christmas.
He said there had been "considerable concern" about the 15-year starting point for judges considering the minimum tariff after knife murder convictions.
"I propose to introduce a new adult starting point of 25 years for murder using a knife or other weapon carried to the scene with the intention of use as a weapon," he said.
"I am determined to do everything in my power to tackle the menace of knife crime on our streets," he added.
Shadow justice secretary Dominic Grieve welcome the increased sentence but suggested that it would be "another empty gesture" without having more police street patrols or enough jail space for those convicted.
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