Legal experts are divided on the need for the Turnbull government's latest swath of terrorism legislation that would allow convicted terrorists to be kept in jail once their sentence ended if they were deemed a risk to public safety.

The legislation, which Prime Minister Malcolm Turnbull hopes to introduce when Parliament returns at the end of August, would effectively treat high-risk terrorists the same as paedophiles and extreme violent offenders who, in certain cases, can already be held as a purely preventative measure after serving jail time.

"The existence of post-sentence preventative detention as a measure will serve as a very real incentive for those imprisoned for terrorist offences to reform. It will provide a very real incentive for people in prison for terrorist offences not to engage in continued extremist activity," Mr Turnbull said at a press conference in Sydney on Monday.

The extended detention periods would be overseen by the courts with regular reports to Parliament on the people subjected to the new system.