The Abbott government is offering asylum seekers on Manus Island and Nauru detention centres up to $10,000 to abandon their hope of resettlement in Australia and voluntarily return to the country they fled from.

The revelation comes as the High Court on Friday issued a stunning rebuke to the Abbott government's border protection policy, striking down its decision to to refuse to issue permanent protection visas to boat arrivals found to be refugees.

In two unanimous decisions, with implications for thousands of boat arrivals, the court ruled that Immigration Minister Scott Morrison's decision to impose a cap on the number of places in Australia's refugee intake for boat arrivals was invalid.