A Victorian Labor MP who has been denied entry to the US while travelling on official parliamentary business, made an official visit to Syria 10 years ago.

Khalil Eideh, who was born in Lebanon, but is an Australian citizen, was barred from boarding a flight to Denver while trying to leave from Vancouver.

It is not known why he was refused entry to the US.

Australian officials are making urgent enquiries and consular staff will provide support if required, a spokeswoman for Foreign Affairs Minister Julie Bishop said.