Malaysia's opposition has rejected the government's argument that it had doubts Australian Senator Nick Xenophon was an official member of a multi-party delegation.
Senator Xenophon was taken into custody at Kuala Lumpur airport on Saturday and told he was banned from entering the country because he had been deemed a security threat.
He was heading the multi-party delegation, which had appointments with a government minister, Malaysia's Electoral Commission and opposition representatives.
Malaysia's Opposition Leader, Anwar Ibrahim, says the government's argument is "frivolous" and that it set up Senator Xenophon's appointments with the government.
"The government is fully-aware of the role of Senator Nick Xenophon," Mr Ibrahim told Australia Network's Newsline.
"He has been here, he has been coordinating with my office as opposition leader.
"This is always, as I have suggested, the state-craft of semi-authoritarian governments. They always commit blunders."
Senator Xenophon arrived home in Melbourne early on Sunday morning, where he told media he would be framing his deportation notice and placing it on his office wall.
He said he was "gobsmacked" when he was "taken away" and detained for nine hours.
"I was told that I was being deported under a certain section of the immigration act which basically relates to being a security risk," he said.
"But it seems the only risk I am is to embarrassing the Malaysian government because of my advocacy for clean elections in Malaysia."
Mr Ibrahim told Newsline that "There's a standard joke here: 'Send out an MP and then welcome the terrorists'."
"You cannot condone a regime that can effectively censor the voice of dissent or the voice of opposition and call it democracy," he said.
Malaysia will hold national elections in April 2013.