Xenophon, a member of the upper house of the federal parliament, has been outspoken on human rights issues in Malaysia and last year claimed to have been tear gassed at a demonstration in Kuala Lumpur.
"I'm effectively a prisoner here," Xenophon said in a telephone call to a newspaper in his Adelaide hometown. "I'm being held in an area with all these holding cells which are full of women.
"They have basically told me I am an enemy of the state. They are trying to get me on the next plane out of here and back home."
Xenophon said he was in Malaysia to join a delegation that had meetings planned with opposition leaders and electoral officers.
He said he was told there were "irregularities" in his passport and taken away by immigration officials when he arrived at the airport.
"I was even meeting members of the government. I mean, the whole situation is ridiculous. We're meant to be the closest of friends with Malaysia," he told the Adelaide Now website.//DPA