CANBERRA – The time asylum seekers spend in Australian immigration detention centres has hit a record high at an average of almost 450 days per person.

The period of detention for asylum seekers in both onshore and offshore centres has blown out under the Abbott and Turnbull Governments, with a steady increase since May.

Government figures show a record high late last year, at an average of 446 days in November and 445 days in December.

There were 23.3 per cent of detainees who spent more than 750 days in detention.

The figures follow a low under the Gillard and Rudd governments, dropping to 72 days in July 2013.

Opposition Leader Bill Shorten said the increase was unacceptable, and that Immigration Minister Peter Dutton had to explain why the processing times increased.

“Labor supports regional processing but the idea that we have got people languishing in Australian facilities, or facilities partly funded by Australia for periods of 450 days on average, is too long,” he said. “Women and children should not be languishing indefinitely.”

Labor’s immigration spokesman Richard Marles also criticised the increases, prompting Dutton to respond with allegations of political “amnesia”.

In a statement, Dutton said that up to 1000 asylum seekers were arriving by boat “at the height of Labor’s incompetence”, leaving a significant caseload for the Coalition Government.

“It will take years to clean up this mess and Labor wiping their hands of a problem they created demonstrates they are not fit for government,” he said.

Dutton also noted the criminal records of some people in immigration detention, as well as those “whose identity has not been verified or who are subject to adverse ASIO assessments”.

Greens Senator Sarah Hanson-Young joined the Opposition in criticism of the extended times, saying in a statement that a new approach to processing was needed.

“We need to have a fair and efficient process put in place to get these people out of detention and integrate them into our community as quickly as possible,” she said.

Senator Hanson-Young said the Greens would continue pushing for legislative changes to put a time limit on detention.

A total of 3251 people remain in immigration detention, with 1459 on Nauru and Manus Island.

More than 150 children were also in immigration detention as of last month, with 91 onshore and 68 on Nauru.

The overall number of detained people has dropped since November, with 10 people leaving offshore centres and 60 less in Australian detention.

Asylum seekers arriving by boat remain the largest proportion of people in detention, accounting for 802 detainees.

The figures coincide with a $1 billion budget blowout by the Department of Immigration and Border Protection, outlined in last month’s mid-year economic and fiscal outlook.

The figures included an additional $499.7 million to manage the legacy caseload of asylum seekers.

A further $342.2 million was allocated over two years for refugee resettlement arrangements for asylum seekers in offshore centres, as well as $213.3 million over four years for the management of the onshore centres.

- ABC