THE UN refugee agency says Australia's immigration detention system is being clogged by growing numbers of rejected asylum seekers who should be sent home.

United Nations High Commissioner for Refugees regional representative Richard Towle says large numbers of people now coming through the asylum system in Australia are not refugees and "the challenge is how to find fair and humane and effective ways of allowing them to leave this country to go home", Fairfax newspapers report.

The deportation of failed asylum seekers has already been announced as central to the government's efforts to stem the flow of boats.

So far, however, only a handful of asylum seekers have been deported. The government is believed to be examining further incentives for people to return home.

Mr Towle told Fairfax that improved political conditions in Sri Lanka and changed methods for assessing Afghan asylum seeker cases have led to the jump in the number of rejected cases, most "left sitting in the detention centres in Western Australia".

He also called for greater regional co-operation and improved conditions in South-East Asia to prevent asylum seekers from making the perilous voyage from Indonesia. He said the problem has little to do with Australia's border protection policies, but rather a "protection vacuum" throughout the region that has been forcing people to risk their lives on unseaworthy vessels.

Originally published as Rejected asylum seekers should 'go home'