Managing arrivals from Sri Lanka has emerged as the biggest challenge for immigration authorities, with the latest boat intercepted at Cocos Island on Wednesday carrying 86 people.

It comes as international pressure builds for a boycott of the Commonwealth meeting to be held in Sri Lanka next year.

More than 5700 Sri Lankans have landed on Australian territory this year, making up more than 80 per cent of all asylum seekers who have arrived by boat.

The Immigration Department has stepped up involuntary deportation of Sri Lankans from the majority Singhalese ethnic group, including 32 on Thursday.

But the number of arrivals continues to outpace deportations and the United Nations has expressed alarm that Australia may not be adequately assessing asylum claims.

Of Sri Lankan asylum seekers already in Australia, the most difficult cases include more than 50 people, the majority Tamils, held in detention.

They have been found to be refugees - preventing them being returned home - but branded a security risk by ASIO, making them ineligible for release into the community.

About 10 men with adverse assessments are being held at the Broadmeadows centre in Melbourne. There have been several suicide attempts this year among the group.

The latest case involves a man - known as Fairfax - who has been detained since June 2009.

He was found early on Thursday morning by another detainee and taken to hospital.

with Ben Doherty

Lifeline on 131 114

beyondblue.org.au