Asked if anyone convicted of terror offences should service their full sentence – as Boris Johnson has now pledged – the Labour leader said: “Not necessarily, no.”
Mr Corbyn said the decision “depends on the circumstances, it depends on the sentence but crucially depends on what they’ve done in prison”.
The prime minister has vowed an end to early prison release for terrorists – and minimum sentences of 14 years – in response to fierce criticism of the freeing of Usman Khan.
But Mr Corbyn said what was crucial was “how our prison services work and what happens to them on release from prison”.
He pointed out that the Parole Board had no involvement in Khan’s release, adding: “There were apparently no probation service involvement in monitoring this former prisoner.”
Mr Corbyn said: “There has to be an examination of what goes on in the prison because prisons ought to be a place where people are put away because of major serious offences, but also a place where rehabilitation takes place.”
During the interview, on Sky’s Sophy Ridge on Sunday, Mr Corbyn also spoke out against removing citizenship from so-called Isis brides in Syria, including Shamima Begum.
“If you strip away their citizenship, where are they going to go?” he asked.
“They are then going to become stateless people roaming around into ungoverned places like in Libya, like in parts of Syria, and they create another terrorist force of tomorrow, Isis or something else.
“Surely, if somebody is a citizen of any one country, then it’s up to that country to take responsibility for them, and that’s why we said that she should be brought back to Britain for questioning, possible charge, but certainly for questioning.”
Rejecting the argument that terror attacks suggested the pendulum had swung “too far”, he said: “You have to create a secure society and you have to defend human rights at the same time.
“If you give up all your democratic and human rights then you have actually given in to those that would take them away anyway.”
Mr Corbyn backed the decision to shoot dead Khan on London Bridge, saying: “I think they had no choice.
“They were stuck with a situation where there was a credible threat of a bomb belt around his body and it’s an awful situation for any police officer, any public servant, to be put in.”