Foreign minister Marise Payne has rejected suggestions Australia is being “dragged into a US political issue” as she defends the decision to assist Donald Trump’s probe into the Mueller inquiry.

Following revelations on Tuesday that prime minister Scott Morrison had agreed to a request from Trump to assist the US justice department’s inquiry into the FBI’s investigation of alleged Russian meddling in the 2016 election, Payne said Australia was behaving as expected of an ally.

“I don’t see it as Australia being dragged into a US political issue,” Payne told ABC radio.

“We’re conducting ourselves as you would expect us to do in these circumstances, we are working in Australia’s interests and we are working with our closest and most important ally.”

When asked what information Australia would be relaying to Attorney General William Barr who is leading the investigation, Payne did not elaborate.

“In terms of material or information that would be exchanged, it is not my practice to comment on the use of intelligence, and secure material but as I said we’ll cooperate as far as we can,” she said.

Labor leader Anthony Albanese called on the government to release the transcript of the call between Morrison and Trump, saying Australians needed a “full explanation” of what he said was an “extraordinary” offer.

“The prime minister needs to just be straight with the Australian people about what’s going on here,” Albanese said.

The government’s defence of its decision comes after revelations in Guardian Australia on Wednesday that Alexander Downer took the then prime minister, Malcolm Turnbull, and senior colleagues by surprise when he relayed information to the American chargé d’affaires in London in July 2016 about his now infamous conversation with George Papadopoulos, then a foreign policy adviser to Trump.

Guardian Australia understands Downer’s conversation with Papadopoulos was recorded in a diplomatic cable back to Canberra.

But the first senior players in Canberra knew of Downer’s conversation with America’s top diplomat in London about Russia obtaining damaging information about Hillary Clinton from her emails was when the Australian government was contacted subsequently by the Federal Bureau of Investigation for more information. That diplomat-to-diplomat conversation, sources insist, was unauthorised.

Controversy about the conversations in 2016 has been revived courtesy of Donald Trump’s appeal to Scott Morrison for Australia’s assistance in an investigation aimed at discrediting the Mueller inquiry.

The New York Times revealed on Tuesday that Trump made the call to Morrison shortly before the Australian prime minister departed for a visit to America last week.

After the call was made public by the Times, Morrison’s office confirmed it. The conversation between the two leaders was, according to a government source, a “polite request” from Trump to cooperate with an investigation being spearheaded by the US attorney general, William Barr.

Barr’s inquiry is an investigation of the investigators. Trump has given the attorney general the unilateral authority to declassify intelligence documents and has ordered the US intelligence community to “quickly and fully cooperate”.

Trump in the call to Morrison sought a point of contact to facilitate Australia’s cooperation with Barr’s investigation. It is unclear what, if any, specific commitments Morrison has made in response to that request.

Downer, a former foreign affairs minister during the Howard era, and at the time of his conversation with Papadopoulos, Australia’s high commissioner in London, told the ABC on Tuesday he had no knowledge of Morrison’s recent conversation with Trump.

“These days it’s not something I am privy to,” Downer told the ABC. “I had a conversation with this guy [Papadopoulos], I passed on one element of the convo to the Americans. There is nothing more to it.”

Labor is demanding answers. “I think Scott Morrison needs to be very clear about the circumstances around this phone call, what was said and whether any agreement was reached in terms of assistance,” the opposition leader, Anthony Albanese, said.

“What Scott Morrison can’t do here is do what he’s had a tendency to do in recent times, which is to dismiss questions which are legitimate from the media as just gossip or as just being in the bubble.

“He needs to actually give some straight answers to what are very clear questions.”

Morrison did not appear before the media on Tuesday. Guardian Australia has contacted Downer for comment about the events of 2016 but the inquiries went unanswered.

Trump is under escalating pressure in Washington with calls for his impeachment triggered by a separate conversation with Volodymyr Zelenskiy, the president of Ukraine. At the root of the gathering impeachment storm in the American capital is a complaint from a whistleblower – believed to be an intelligence official – that Trump was using the power of his presidential office to solicit interference from a foreign country in the 2020 election.

It is unclear why Trump contacted Morrison in advance of his visit to secure Australia’s cooperation with the Barr investigation rather than raising it during the prime minister’s time in Washington.

Morrison dead batted a reporter’s question during his visit about whether Downer had come up. “Well I’m not going to go into private conversations but what we were discussing yesterday were issues about our strategic relationship from trade,” he said. “The frontier technologies, our defence relationships, these were not issues that were there for discussion.”

The dialogue between the Trump administration and the Morrison government about cooperation with the Barr investigation has apparently been playing out for some months.

On 25 May, Trump blasted Australia before leaving on a trip to Japan, declaring he wanted Australia’s role in setting off the FBI inquiry into links between Russia and his election campaign examined by Barr. Trump said he hoped Barr would “look at the UK and I hope he looks at Australia and I hope he looks at Ukraine. I hope he looks at everything, because there was a hoax that was perpetrated on our country.”

Australia’s foreign affairs minister, Marise Payne, then signalled the government was prepared to contribute to the Barr investigation. Payne said at the time Australia had not yet been asked but “we would, of course, consider such a request were it to be made”.

After Trump’s comments, Australia’s ambassador to the US, Joe Hockey, wrote to Barr, copying in the White House chief of staff, Mick Mulvaney. In a letter released by the Australian government on Tuesday after the New York Times report, Hockey said: “The Australian government will use its best endeavours to support your efforts in this matter.

“While Australia’s former high commissioner to the United Kingdom, the Hon Alexander Downer, is no longer employed by the government, we stand ready to provide you with all the relevant information to support your inquiries.”