One Nation senator Malcolm Roberts lobbied Australian diplomats in Washington for tickets to US President-elect Donald Trump's inauguration, prompting them to ask Congressional offices for spare tickets.

Official tickets to the January 20 ceremony are highly sought after and members of the US Congress are free to distribute a number of tickets at their discretion.

One Nation leader Pauline Hanson said she had been "gifted" an invitation to the inauguration, claiming it was a surprise and an honour.

Senator Roberts said he would attend the event "as a guest of the US Government" and said he and Senator Hanson had received invitations, while the Prime Minister Malcolm Turnbull had not.

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But in a statement, a Department of Foreign Affairs and Trade said diplomatic staff were tasked with finding the senators tickets after a number of requests from the party.

"Following multiple requests from Senator Roberts, the Embassy in Washington asked a number of Congressional offices if they had any spare tickets available," he said.

"On 13 January, Congressman [Adam] Kinzinger's office advised they had two tickets available."

Senator Hanson has declined to attend the inauguration because it clashed with work commitments while Senator Roberts will stay at home, recovering from a medical operation.

One Nation senator Brian Burston will now attend the inauguration representing the party.

On social media, Senator Roberts claimed he never said he was invited to the inauguration, but had instead received invitations.

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In response to Greens senator Nick McKim, he said "you just had to ask the right people" to receive an invitation to the inauguration.

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In a statement, a DFAT spokesman said it was tradition for the heads of diplomatic missions to represent foreign governments, rather than political leaders.

"The US State Department has advised that as in the past, foreign delegations will not be invited to Washington for President-elect Trump's 2017 inauguration and that heads of state and governments will be represented by chiefs of diplomatic missions in Washington," the statement said.

"Ambassador Joe Hockey will attend this event.

"Tickets are required to view the ceremony from designated viewing locations, and are allocated through normal practice to Members of Congress and others to distribute."

The DFAT spokesman said the tickets were not yet available for collection.

According to a report by Buzzfeed, Mr Kinzinger has distanced himself from One Nation and stressed he does not endorse any political party in Australia.

One Nation leader Pauline Hanson dismissed questions about the tickets, ahead of a campaign trip to Western Australia.

"That probably is fake news," Senator Hanson told reporters at Perth Airport.