The Department of Foreign Affairs and Trade (DFAT) is facing calls for its incoming advice to the federal government to be made public.

So-called "red books" already have been released by the Attorney-General's Department and treasury but DFAT has refused to publish its briefing, claiming it is classified.

The red books released so far have being redacted by security officials.

"Earlier this year, DFAT agreed to release a briefing provided to incoming secretary Dennis Richardson," Liberal senator Russell Trood said.

"One wonders what could possibly be in the red book that would make it more sensitive than the briefing provided to the department secretary."