PNG should have known of posting: DFAT

The secretary of the department of foreign affairs has admitted Papua New Guinea wasn't told about the government's plan for Bougainville post.

The secretary of the foreign affairs department has conceded there was "miscommunication" with Papua New Guinea over a planned Australian diplomatic mission in Bougainville.

PNG prime minister Peter O'Neill was shocked by the May budget announcement, saying he hadn't been consulted by Canberra.

Department secretary Peter Varghese told a Senate committee in Canberra on Wednesday the plan should have been conveyed to Mr O'Neill and his foreign minister, but "regrettably" neither could be reached.