A racial discrimination trial launched by Greens deputy leader Mehreen Faruqi over a tweet made by Senator Pauline Hanson telling her to "piss of back to Pakistan" will hear evidence the One Nation Leader is a "well-known, long-standing and prolific sayer of racist things".

Senator Faruqi claims Senator Hanson violated section 18C of the Racial Discrimination Act when she tweeted in 2022 that she should "pack your bags and piss off back to Pakistan".

Senator Hanson posted the tweet on the day of Queen Elizabeth II's death in September 2022, after Senator Faruqi called for a treaty with First Nations and said she could not mourn "the leader of a racist empire built on stolen lives, land and wealth of colonised people".

Sue Chrysanthou SC, representing Senator Hanson, told the court her client does not dispute the tweet represented the One Nation leader's beliefs but instead argued that Senator Faruqi's tweet was intended to "offend and provoke a response".

In his opening statement on day one of the five-day-long trial, Senator Faruqi's lawyer Saul Holt KC told the Federal Court they would seek to prove the comment was racially motivated by providing evidence from "over decades" that Senator Hanson has said "racist things".

"The examination of Senator Hanson's tendency to be racist, and to say racist things over decades leads inextricably to the conclusion that this wasn't just said because Senator Faruqi was a migrant … rather it was said at least in part because Senator Faruqi is a Muslim, non-white and from an Asian country," Mr Holt said.

Section 18C of the Racial Discrimination Act states that it is unlawful for a person to commit a public act that is reasonably likely to offend, insult, humiliate or intimidate another person or a group based on the race, colour, or ethnic origin of the other person.

Senator Faruqi's legal team argued Senator Hanson's tweet was "not limited to the persons to who its directed at" but also resulted in "vicarious racism" against people with similar attributes to her.

"Those words … tell a person, here Senator Faruqi but also others who have the same characteristics or share some characteristics with her, that they are not welcome in Australia," Mr Holt said.

Senator Faruqi emigrated to Australian from Pakistan in 1992 and became Australia's first Muslim senator when she joined the Senate in 2018 after having served in the New South Wales parliament.

Mr Holt told the court Senator Hanson's tweet "predictably" unleashed tweets from others expressing a similar sentiment.

He read multiple replies to Senator Hanson's tweet to the court, including one which said: "Well done Pauline, make sure she gets on that plane, or she might slip out the back."

Mr Holt said the "torrent of abuse" made her question her place in Australia and that she continues to have "sleepless nights" over the ordeal.

Ms Chrysanthou told the court the Greens senator received a "barrage of criticism" online and from the media, five hours before Senator Hanson tweeted her response.

"The barrage arose and started because of her tweet, not my client's tweet," Ms Chrysanthou said.

"If the person enters the affray in such a provocative way, they expect and seek out a response."

Ms Chrysanthou said her client's tweet was a matter of public interest and this case seeks to impede Senator Hanson's "political freedom".

The court heard Senator Hanson's lawyer will seek to prove Senator Faruqi is "a hypocrite and only against certain forms of racism".

The court heard Senator Faruqi was not seeking damages but was asking the court to order Senator Hanson to donate to a charity, attend a course, delete the original tweet and publish a new post acknowledging she has "committed unlawful offensive behaviour" and pin it to her profile for three months.