Amnesty International has implored Australia to begin processing the 387 asylum seekers it sent to Nauru and to rethink its strategy of detaining boat arrivals there.
It describes conditions at the island's camp as completely unacceptable.
The Sydney Morning Herald says an Amnesty delegation expressed shock at the conditions at the camp after being given access on Tuesday.
It says the conditions are tougher than at any mainland detention centre and are responsible for what it calls a terrible spiral of self-harm, hunger strikes and suicide attempts.
A spokersperson Graham Thom says processing has to start straight away, or at least people need to be told when it's going to start and how long it will take.
Dr Thom says up to 14 men are living in cramped conditions in single tents.
He says it is very hot and humid, the tents leak and bedding gets wet.
But a spokesperson for the Immigration Minister, Chris Bowen, says conditions in Nauru at times may not be pleasant, but immigration staff and service providers are working in the same environment.