Family members among 157 asylum seekers being detained on the high seas in separate rooms on a customs vessel are allowed out for meals and ''approximately three hours'' of daylight a day, according to a document lodged with the High Court on Tuesday.

While it was previously stated 153 asylum seekers were on a boat that was intercepted off Christmas Island more than three weeks ago, the document says there are 157.

Scott Morrison arriving for talks with India's Minister for Home Affairs, Mr Rajnath Singh. Credit:Jason Koutsoukis

A document filed by the government reveals the national security committee of cabinet decided on July 1, two days after the boat was intercepted, that those on board ''should be taken to a place other than Australia''.

The document says the asylum seekers are permitted ''approximately three hours' outside during the day in natural light for meals'', but says it would be unsafe to give them unrestricted movement.