Australia is seeking further explanation from Malaysia about why an Australian senator, who went to politically sensitive Malaysia to discuss electoral reform, was denied entry and deported, Prime Minister Julia Gillard said on Sunday.
Malaysia refused entry on Saturday to independent Senator Nick Xenophon, with an immigration official saying the decision was made because he had participated in an illegal street rally for electoral reform in the Southeast Asian country last year.
The Malaysian government is bracing for an election within months that is expected to be the closest in the former British colony's history.
"We made immediate and strenuous representations on his behalf, not only in relation to him being detained, but into him being allowed to be in Malaysia," Gillard told reporters in Melbourne, where Xenophon had arrived earlier on Sunday.
"Clearly we didn't succeed. We will continue to pursue this issue with the Malaysian government."
Xenophon was part of an unofficial delegation seeking to discuss the coming elections with members of the Malaysian government, opposition, judiciary and election commission. The other three members of the delegation cancelled their trip after Xenophon was detained on arrival in Kuala Lumpur.
He said he had been told he had been detained because he was considered "a security risk". The Malaysian government said he had broken the law on a previous visit.
Xenophon was invited to Malaysia last year by opposition leader Anwar Ibrahim and observed a major street rally for electoral reform in April that ended in violence. He later criticised the government's handling of the rally.
Anwar, a former deputy prime minister, wrote on his blog on Saturday that Malaysian Prime Minister Najib Razak should not treat visitors as "enemies of the state" because they had criticised the ruling United Malays National Organisation.
"While it is true that senator Xenophon has raised concerns about the probity of our coming general elections, he has neither violated any written law nor conducted himself in a manner which may be constituted as a threat to our society," Anwar said.
Razak must call the election by the end of April and the opposition holds a good chance of toppling UMNO, the anchor of a Barisan Nasional coalition government, after 56 years in power.
That prospect is unnerving some government officials, emboldening the opposition and raising risks for investors.
Australian Foreign Minister Bob Carr said he had contacted his Malaysian counterpart, Anifah Aman, over Xenophon's deportation but did not think ties would suffer.
"He said Malaysia took strong objection to foreigners interfering in their election campaign," Carr told reporters.
Australia and Malaysia have had a sometimes rocky diplomatic relationship. The two countries clashed 20 years ago when former Australian Prime Minister Paul Keating called former Malaysian leader Mahathir Mohamad "recalcitrant" for boycotting the 1993 Asia-Pacific economic forum.