THE 16-month delay in the United States posting an ambassador to Canberra is a sign that Australia has been “downgraded”, says former deputy prime minister Tim Fischer.

The Australia-US relationship is again under the microscope after The New York Times revealed Canberra’s top envoy in the UK, Alexander Downer, helped spark an FBI investigation into Russia’s role in the US election.

Mr Fischer told Fairfax Media on Tuesday that the delay in the US posting an ambassador to Australia is a sign of tensions between the nations.

The US has not replaced its former ambassador to Australia, John Berry, since he left the post in September 2016.

Deputy chief of mission James Carouso has acted as ambassador since September 2016 but Admiral Harry Harris is tipped to be the next US ambassador to Australia.

“This is now bordering on a diplomatic insult,” Mr Fischer said. “We’ve been downgraded, despite all the nice noises. We are a low priority.”

Acting Labor leader Tanya Plibersek today said it would be “very disappointing” if Australia was not a priority for the Trump Administration.

“It is a concern that we still don’t have a full time ambassador from the United States,” she said.

“It is a very important relationship between Australia and the US.”

Ms Plibersek said she did not want to inflame tensions but added: “It is certainly desirable to have a full time appointment sooner rather than later.”

The acting Labor leader also took a swipe at the Turnbull Government’s handling of relations with other key allies and trading partners.

“We’ve been recently in some degree of official conflict with the Chinese government, unbelievably we’ve had a Foreign Minister attacking the government of New Zealand, we’ve had all sorts of quite awkward periods in our relationships with our major trading and diplomatic partners in recent times,” she said.

Prime Minister Malcolm Turnbull has said he is not worried about the Alexander Downer saga damaging his relationship with US President Donald Trump, but Labor wants an explanation into the Australian diplomats’ involvement in the FBI investigation.

Trump campaign adviser George Papadopoulos told Mr Downer during a meeting in London in May 2016 that Russia had thousands of emails that would embarrass Democratic candidate Hillary Clinton.

Australia passed the information on to the FBI after the Democratic party emails were leaked, according to the Times, which cited four current and former US and foreign officials with direct knowledge of the Australians’ role.

Joe Hockey headed up Australia’s dealings with the FBI, Fairfax reports.

The prime minister’s personal relationship with Mr Trump got off to a rocky start with a heated phone call over the US refugee resettlement deal a year ago.

Mr Fischer said that tensions over the resettlement deal are to blame for the lack of ambassador to Canberra.

The post has been empty since September 2016.