Labor senator Kim Carr accused the minister of making a blanket ruling on the documents rather than reading each one before ruling it not be disclosed.

Senators probed an apparent discrepancy over the definition of individual asylum seekers as ''illegal maritime arrivals'' or ''IMAs'' after Mr Morrison said there had been ''zero arrivals since December 19''. An arrival, Mr Morrison said, constituted an asylum seeker being "transferred into immigration authorities".

Asked how many boats had entered Australian waters during the same period of "zero arrivals", Mr Morrison refused to respond. To do so, he maintained, would be against the public interest.

Earlier, Mr Morrison had boasted that the government's tough policies which include turn-backs and off-shore processing, was working because it had delivered the first IMA-free calendar month in 58 weeks and the first January of zero boats since 2006.

An argument ensued as Labor and Greens senators attempted to establish if the zero-IMA claim was sustainable only because the definition of an arrival excluded people aboard vessels turned around at sea, even where they had clearly entered Australian waters. In the government's weekly statement later in the day, it was revealed one asylum seeker was transferred to Christmas Island during the week due to a health condition.