Lawyers fighting over the future of 153 asylum seekers detained at sea have been told to “get on with it” in the High Court.

Australian government lawyers are fighting to keep secret documents used in the decision to detain 153 asylum seekers at sea.

Commonwealth barrister Stephen Donaghue QC told the High Court that some documents would be subject to public interest immunity, meaning they would not have to be revealed in court.

The asylum seekers have been detained on the high seas, outside Australia’s migration zone, since their boat was intercepted on its way from India on July 7.

Dr Donaghue could not say whether the government would admit or deny a decision had been made to take the asylum seekers to a place other than Australia.

Human Rights Law Centre executive director Hugh de Kretser said there was “extraordinary secrecy” around the government’s decisions.

“(The asylum seekers) simply ask, through this case, that those decisions be made fairly,” Mr de Kretser told reporters in Melbourne on Friday.

Dr Donaghue said the government had no plans to send the asylum seekers to Sri Lanka, and would stick to its undertaking that no one on the boat would be sent to another country without three days written notice.

Mr de Kretser said that was at least a positive result for the asylum seekers.

“It’s a shame it took two weeks of detention and a High Court case to produce that clarification, but it’s nonetheless welcome,” Mr de Kretser said.

Justice Kenneth Hayne said given the asylum seekers were in custody, it was important the legal battle over their future was finished as quickly as possible.

“The parties are just going to have to bend their back to get on with it,” Justice Hayne said.

“I am not going to let this case devolve into a procedural morass. There’s got to be some sense shown.”

Justice Hayne said the case appeared to come down to whether the Australian government had the power to intercept the asylum seekers and take them to a country other than Australia.

He adjourned the case until Tuesday.