A review into the killing of Tory Sir David Amess found inquiries into his attacker, Ali Harbi Ali, were dropped by the Prevent anti-terror programme too soon.
Mr Jarvis said: "The assessment in terms of the perpetrator's vulnerabilities was problematic and this ultimately led to questionable decision making and sub-optimal handling of the case during the time he was engaged with Prevent and Channel.".
Security Minister Dan Jarvis told MPs a review had found "problematic" failings, and warned the assessment of the risk Ali posed was "sub-optimal".
The Government minister told MPs that Ali - who was given a whole-life sentence in 2022 aged 28 - was referred to Prevent, and the specialist Channel anti-extremism programme in 2014.
Mr Jarvis said: "It (the review) identified that the vulnerability assessment framework was not followed with the perpetrator's symptoms being prioritised over addressing the underlying causes of his vulnerabilities.
