Australia's government has called on the United States to explain why a politician with dual Australian-Syrian citizenship was refused entry last week.

Victoria state MP Khalil Eideh, a 62-year-old who was born in Lebanon to Syrian parents, was travelling with other politicians on government business when he was prevented from flying from Vancouver, Canada, to Denver, Colorado.

"At the foreign minister's request, Australia's embassy in Washington made urgent inquiries of the US authorities as to what happened, and why Mr. Eideh was refused entry to the United States last week," Foreign Minister Julie Bishop's office said in a statement on Tuesday.

"The US authorities are following up on our request for information."

Having returned to his hometown of Melbourne on Saturday, Eideh told reporters that he had been "discriminated against".

"I'm very, very disappointed and frustrated," he added.

'No explanation'

Eideh said he had a US visa and was given no explanation for why he was denied entry.

"To me, it is unacceptable, because I'm representing the Australian people, the Victorian people," he said.

The US Customs and Border Protection agency did not immediately respond to a request for comment on Tuesday.

Eideh had a US visa and was part of a group of Victoria politicians examining the effectiveness of drug laws and regulations in Europe and North America.

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US President Donald Trump's Muslim ban went into partial effect in June.

Under the ban, visitors from Iran, Libya, Somalia, Sudan, Syria and Yemen must prove they have a "bona fide relationship" to a US person or entity to be allowed entry to the US.

The ban has faced a number of court challenges since a revised version was announced by the Trump administration in March.