The federal opposition says Immigration Minister Peter Dutton is "a disgrace" after Fairfax Media revealed a dramatic blowout in the time people languish behind wire in immigration detention.

But Mr Dutton said he is dealing with Labor's legacy of asylum seekers, and many of those in detention pose security risks and should not be released.

Immigration minister Peter Dutton. Credit:Andrew Meares

The latest statistics from the Department of Immigration and Border Protection show that in December, men, women and children in onshore immigration detention had been there for an average 445 days. In November, the figure was 446 days.

The figures prompted concern from Human Rights Commission president Gillian Triggs, who said medical evidence consistently showed that prolonged detention "can do serious mental harm".