Xenophon questions AFP Bali Nine answers

Federal police faced an agonising decision but they should have arrested the Bali Nine drug smugglers in Australia, independent senator Nick Xenophon has argued.

He has queried an Australian Federal Police explanation of its role in the investigation that led to the executions of ringleaders Andrew Chan and Myuran Sukumaran last week.

He says the "largely unanswered" question is why the group was arrested in Indonesia and not Australia.

"Without that answer there can be no surety that this will not occur again," Senator Xenophon told reporters in Canberra.