Labor's Louise Pratt has branded members of her party "extremists" and said they exercised a power far in excess of their numbers during her valedictory speech in Federal Parliament.

Senator Pratt will leave the Senate at the end of the week after Labor powerbroker Joe Bullock claimed the top spot on the party's ticket in last year's Senate election.

She described herself as "proudly" on the left of her party, but said those with her views were characterised as "radicals".

"I have always found it ironic that the very views that lead to me being labelled exactly that are those views shared by the majority of the Australian population, although quite often not by the majority of the Australian Parliament," she said.

She also used the opportunity to reaffirm her commitment to reform of the Marriage Act to recognise same-sex unions and legal access to abortion.

"Despite attempts to characterise views such as mine as ‘radical’, every piece of research in this country demonstrates that these views are shared by the majority of Australians," she said.

"They are mainstream views and it is those who deny them that are extremists in our country.

"It remains a great disappointment to me that my Party still contains a small rump of those extremists, who exercise, in my view, power far in excess of their number, and most certainly far in excess of their support among our Party’s members and the among our Party's unions."

She spoke about the need to ensure public confidence in Australia's electoral processes.

She said the 2013 election, recount and subsequent re-run had undermined public trust in the electoral system, and urged her colleagues to work to restore that confidence.

"My own personal disappointment is a minor thing when set beside the potential for those events to undermine that trust and confidence in electoral processes which underpin the legitimacy of our Parliaments and our Governments," she said.

"Fair, transparent, and democratic processes within political parties are as important for the integrity of the system as are fair, transparent and democratic elections.

"I won't be here in this place to be part of the discussions and debates about what steps need to be taken to ensure that what happened in 2013 never happens again."

Speaking at a function arranged by the Dawson Society in November last year, Senator Pratt's election running mate Mr Bullock described her as a poster child for causes such as gay marriage and accused her of canvassing votes against him.

After details of the damaging speech were aired in the media this year, Mr Bullock issued a public and "unreserved" apology to Senator Pratt and the Labor Party.