SYDNEY - An Australian lawmaker deported from Kuala Lumpur said Sunday his expulsion was ordered by the "highest levels" of the Malaysian government over his push to promote free elections in the Southeast Asian nation.

Outspoken independent Senator Nick Xenophon, who was detained and barred from entering Malaysia upon landing in Kuala Lumpur on Saturday, said he was whisked away to an interrogation area and told he was a security risk.

"It is clear that I was deported because of my advocacy for the pro-democracy movement in Malaysia, in particular the (electoral reform) group Bersih," Xenophon told reporters after arriving at Melbourne airport on Sunday morning. "It was unexpected, I was quite gobsmacked... It seems the only risk I am is to embarrassing the Malaysian government because of my advocacy for free elections in Malaysia," he added.

Xenophon said lawyers had informed him that "this order was made at the highest levels of the Malaysian government", with the prime minister's office as its probable source.

"But that's just speculation, that's for Malaysia's prime minister's office to confirm or deny."

The senator said he was put on an indefinite "do not enter" list by Malaysian officials, which he described as "ominous". Xenophon has previously travelled to the country several times, including to study the polling system at the invitation of opposition leader Anwar Ibrahim.

On this trip he was part of an Australian parliamentary delegation and was due to meet members of Bersih as well as senior government officials, including some from the Election Commission.

 The other lawmakers cancelled their trip after he was detained.

Xenophon questioned why, if he was seen as a security risk, had he been able to schedule meetings with senior officials including parliamentary affairs minister Mohamed Nazri Abdul Aziz.

Australian Prime Minister Julia Gillard said she was "surprised and disappointed" by the Malaysian response, adding that Canberra had made "immediate and strenuous representations on behalf" of Xenophon.

"Clearly we didn't succeed in getting the agreement of the Malaysian government for him to remain in Malaysia," said Gillard. "We will continue to pursue this issue with the Malaysian government."

Foreign Minister Bob Carr said he had spoken directly with his Malaysian counterpart who told him "they did not want foreign interference in their election process".

He stressed Xenophon and the other parliamentarians had been travelling as private citizens, not Australian government representatives.

Malaysia's opposition and rights groups have also condemned the deportation. Prominent human rights group Suaram said it was "totally arbitrary and politically motivated".

National elections, due by June, are expected to be the toughest ever test for Prime Minister Najib Razak's coalition, which has ruled Malaysia since independence from Britain in 1957 but has lost support in recent years.