The man accused of raping a colleague in Australia's Parliament House in Canberra has gone on trial.

Former political staffer Bruce Lehrmann is charged with sexually assaulting Brittany Higgins in the office of a government minister in March 2019.

Mr Lehrmann, 27, has pleaded not guilty and denies the pair had sex at all.

The trial in a Canberra court is scheduled to last up to six weeks and could call on several high-profile witnesses.

Opening their case on Tuesday, prosecutors said the alleged incident had happened after "a drunken night out" with colleagues.

Mr Lehrmann and Ms Higgins had stopped at Parliament House, where they both worked, and Ms Higgins soon fell asleep on a sofa in a minister's office, the jury was told.

"The next thing I can remember was being on the couch as he was raping me," Ms Higgins said in a police interview played to the court.

"I said 'no' at least half a dozen times. He did not stop.

"I was crying through the entire process."

The Australian Capital Territory Supreme Court heard Ms Higgins had consumed 11 drinks earlier that night and, in the days after, had described herself as "barely lucid" and so intoxicated "I couldn't write my own name".

She initially reported the incident in April 2019, but the court heard she withdrew her complaint because she feared it would interfere with her job during an election campaign.

Almost two years later, in February 2021, she asked police to reopen the case after conducting interviews with two journalists.

But Mr Lehrmann's barrister, Steven Whybrow, said Ms Higgins's account of events contained holes and inconsistencies.

He said it was "the elephant in the room" that Ms Higgins went to the media before making her 2021 request to police - and he urged jurors to ignore previous media coverage which he said had snowballed.

He said her allegations had "rocked the entire political landscape".

"Mark Twain once said: 'Never let the truth get in the way of a good story.' And this case is the epitome of that phrase," the barrister said.

Mr Lehrmann remained entitled to the presumption of innocence, he added.

Chief Justice Lucy McCallum also warned jurors the case had received "a fair measure of media publicity" but that it was "very important" they put this out of their minds.