Labour leader Phil Goff is standing by his long-time friend, South Australian Premier Mike Rann, as he fights for his political life after allegations of an affair with a married parliamentary barmaid.

Mr Goff said he believed Mr Rann's complete denial over the barmaid's claims to have had sex in his Parliamentary office.

Mr Goff, friends with Mr Rann since they attended Auckland University together in the 1970s, said he accepted Mr Rann's version in the classic "he says-she says" controversy.

"I've known Mike for a long time. He is a person of integrity. There is no reason for him to deny this if it were true - he was a single man at the time it was before his engagement," said Mr Goff.

Mr Goff criticised Channel Seven and the Australian New Idea which had broadcast and published Michelle Chantelois.

"I think before anybody in the media runs a story with this sort of allegation and innuendo, they need to make sure their facts are right - and I don't think they are in this case."

Mr Rann came to New Zealand in September to deliver a speech to the Labour Party conference that endorsed Mr Goff's leadership.

Mr Rann, who was educated in New Zealand, went to primary school with Mr Goff's wife Mary Goff in Mangakino in the 1960s.

He told stories of riding on the back of Mr Goff's Norton Commando motorbike and holidaying in the South Island together.

Yesterday Mr Rann described the allegations against him as absolutely false and motivated by political malice.

"I have not had sex with her and the idea that I would have sex between meetings in my office in Parliament Office while Parliament was sitting is so patently ridiculous, I would have thought all of you would have known this," he told reporters.

"I can say today that I'll be taking legal action against Channel Seven and New Idea for allegations that are totally, absolutely, untrue."

Mr Rann is Australia's longest-serving premier and will be running for a third term next March.

Suggestions of an affair with Michelle Chantelois first emerged last month after her estranged husband, Richard Phillips, allegedly struck Mr Rann in the face with a rolled-up magazine at a public function, yelling "remember my wife".

Mr Rann denied knowing Mr Phillips, who was charged and will appear in court in two weeks, but said he and Ms Chantelois had shared a close, platonic friendship for several years.

Until Sunday night Ms Chantelois had refused to comment on the friendship. She was paid a reported A$200,000 ($243,000) for the interview, although the amount has not been confirmed.

Mr Rann's political future now depends on making a more convincing argument than Ms Chantelois who, in the absence so far of any supporting evidence, is now locked in a "he said, she said" argument.

Under Mr Rann both the Labor Party and the state have prospered, reflected in the Premier's political longevity and his performance in the polls.

Although his personal standing has been dented in the past two years, Mr Rann's approval rating in July, the most recent Newspoll, still ran at 51 per cent against a dissatisfaction rating of 40 per cent.

Over the same period Labor's two-party preferred vote has nudged upwards, and in July led the Opposition in Newspoll by 56 per cent to 44 per cent.

Senior Labor figures have publicly supported Mr Rann, although some warned if Ms Chantelois' allegations were proven that support would evaporate.

A rough guide to public reaction came in an internet poll by AdelaideNow, which showed almost 60 per cent of those voting believed Rann should step down.

Ms Chantelois' lurid allegations detailed an affair that had started with flirting in the parliamentary dining room in 2003 and rapidly progressed to sex in the Premier's office, at a golf course and at his home.

"I was falling under his spell," she said. "The relationship was intoxicating. It was like a drug and I was addicted.

"I knew it was wrong but I couldn't stop doing it."

Ms Chantelois said Mr Rann had set strict rules: no falling in love, put nothing in writing.

The two communicated by text messages and, Ms Chantelois alleged, made passionate love. "I was just drawn into doing whatever it was that Mike Rann wanted me to do and just the whole intensity of the relationship."

She said Mr Rann fantasised about her underwear and had asked for her measurements so he could buy her "sexy bras and panties".

Once he had asked to her to watch the movie Unfaithful and had later acted out one of the scenes in his office. "The kissing immediately started. He pushed the furniture aside and that's where it occurred, on the floor in his office."

Ms Chantelois said money was not the motivation for her disclosures - "I couldn't go to my grave with these lies" - and said it was time Mr Rann took responsibility for his actions.

Mr Rann said the allegation that he had sex on the floor of his parliamentary office between meetings was absolutely ridiculous and absurd.

"My office is like a train station, the revolving door on Grand Central stop," he said.

"I'm constantly surrounded by advisers, MPs come in and out, ministers come in and out, staffers come in and out, members of the Opposition come in and out.

"The suggestion that I would have sex on a golf course in Adelaide as a fairly visible citizen of this state is totally, absolutely ridiculous.

"So I reject these allegations ... I have not had sex with her."

He said he had never hidden the fact that he had a friendship with Ms Chantelois, which had ended before his engagement to his wife Sasha Carruozzo.

He said Ms Carruozzo knew the full details of the relationship and had no concerns about it.

"That friendship was based on confidences and discussions, it was funny, it was flirty, just like any other friendship would be.

"But there is a real, real difference between that friendship and what she has said."

Mr Rann said he did not know why Ms Chantelois had made the allegations.

"I can only assume that she's gone through hell over the past four years [after their friendship ended in 2004], and of course her husband is before the courts two weeks from now," he said.

"It's not for me to speculate, but I do not intend to denigrate her in any way whatsoever."

Mr Phillips also spoke to the media yesterday, reading a prepared statement in which he called for a parliamentary inquiry into his estranged wife's allegations. "It is my opinion that Mr Rann took advantage of my wife's youthful naivety during a very difficult time in our lives and marriage," he said.

"He has shown that he lacks the personal qualities and character to remain in the office of Premier [and] I now call for a parliamentary inquiry into the matter."

MIKE RANN Born: In 1953 in Britain. Emigrated to New Zealand in 1962.

Educated: MA, University of Auckland.

Married: Sasha Carruozzo in July 2006. Two children from a previous marriage.

Media career: Was a journalist with the NZBC before moving to South Australia in 1977 to become press secretary, speechwriter and adviser to three South Australian premiers.

Political career: Elected to South Australian Parliament in 1985. Cabinet minister from 1989-93. Leader of the Opposition from 1994-2002. Premier since 2002. Re-elected in March 2006.

2009: NSW Health Minister John Della Bosca resigns after his six-month affair with a 26-year-old woman is revealed.

2008: Western Australian Opposition Leader Troy Buswell resigns from the leadership position after admitting to sniffing the chair of a female Liberal staffer.

2002: Former federal Foreign Minister Gareth Evans admits to having had an affair with former Australian Democrats leader Cheryl Kernot who left the Democrats to join the Labor Party.

2002: Former federal Treasurer Jim Cairns admits to having had a sexual relationship with his principal private secretary Junie Morosi despite denials in a 1982 defamation case.

1987: Former federal Opposition leader Billy Sneddon suffers a fatal heart attack while having sex with his son's ex-girlfriend.

1987: Hawke Government minister John Brown becomes infamous for making love to his wife Jan on his parliamentary desk.

1951: Former Prime Minister Ben Chifley suffers a heart attack and dies while in the company of his secretary. Claims later emerge that Chifley had a long-running affair with the woman.