Outgoing Liberal Senator and former minister Nick Minchin has used his Senate valedictory speech to highlight some of the wins and losses of his career.

Senator Minchin retires this week after 18 years in the chamber, and singled out his role in defeating the referendum on Australia becoming a republic as one of the best moments of his career.

He also lamented he was not able to convince John Howard to retire on the 10th anniversary of his prime ministership and admitted to being surprised by the opportunities he has had, describing his lot as "a fortunate political life".

"Unburdened by the levels of ego and ambition which weigh heavily upon so many of our colleagues in the other place, I've instead been the beneficiary of chance, luck and being in the right place at the right time," he said.

Senator Minchin is one of 12 senators who did not contest or were not re-elected at the last election. This week is their last in the chamber as their terms expire at the end of the month.

Senator Minchin talked about the difficulties of being the government's leader in the Senate during the Howard years.

"Can I say that managing a one-seat Coalition government majority in this place for two years was particularly challenging, and thank you Barnaby [Joyce] for that," he joked.

On career highlights, he nominates his time as finance minister, six years of successive surpluses and the setting up of the Future Fund.

He also listed his role in the 1999 referendum on the republic as a major plus.

"Nothing in my long career in campaigning has given me greater pleasure than the comprehensive rejection of that republican model," he said.

"One cause I will remain actively involved in after I leave this place is advocacy of the virtues of our current constitutional arrangements."

But he also lamented some failures.

"I've failed to have the courage of my conservative convictions concerning my serious reservations of the time about the US plans for the invasion of Iraq," he said.

"And I do hope the Coalition understands the lesson of our 2007 defeat; that the Australian people will only ever accept incrementalism, not radicalism when it comes to industrial relations reform.

"And finally I regret my incapacity to create the circumstances in which John Howard might have seen the wisdom in retiring on the occasion of the 10th anniversary of his prime ministership in March 2006."

A self-professed climate change sceptic, he also talked about carbon emissions.

"I must say when I first learned of the existence of the Australian Greenhouse Office, I assumed it was responsible for supplying tomatoes to the Parliament House kitchen," he said.

"But no, as I soon learned as industry minister, it was in fact a government-funded redoubt of veritable soldiers in a war against carbon dioxide.

"Thus upon leaving the Parliament I'm contemplating the foundation of an organisation called the Friends of Carbon Dioxide.

"Membership will of course be open to all, including the plants whose very existence depends on CO2."

He paid tribute to colleagues on both sides of the chamber, as well as his family.

He also delivered this advice to current and future politicians.

"Remember the virtue of earning the respect of your colleagues on all sides of the chamber," he said.

"Earn their respect for your integrity, your decency, your passion, your commitment to your ideals and your willingness to do unto others as you would have them do unto you."

More goodbyes

Senator Alan Ferguson is also leaving Parliament after 19 years. The one-time Senate president used his farewell address to suggest it was time to reform or junk Question Time.

"If it was up to me I would abolish Question Time as it is currently structured," he said.

"It is a total waste of time and dare I say it, not much better in the other place, if not worse.

"We have in the Australian Parliament the worst Question Time of any other parliament that uses the Westminster system throughout the world."

Liberal Senator Julian McGauran used his outgoing speech to describe how his heart sank when Prime Minister Julia Gillard moved to reject an amendment on human embryo research.

Senator McGauran is a devout Catholic who entered parliament in 1987 as a member of the National Party but became a Liberal in 2006.

He says the most disappointing moment in his parliamentary career was when Ms Gillard rejected an MP's attempts to stop the use of female baby's immature eggs to create experimental embryos.

"The very instant that Member sat down, literally, the charge to defeat this amendment was lead by Ms Julia Gillard," he said.

"I was chilled by the adamant tone and the agitated demeanour against such a decent proposal as this."

Government Senate leader Chris Evans praised Senator McGauran for his long-running campaign for the independence of the people of East Timor.

"Julian McGauran, I think, has a very proud record in terms of East Timor," he said.

"Too many people were prepared to be apologists; Julian really campaigned strongly for the East Timorese people against the views of both political parties and its to his enduring credit that he provided support for the struggle of the East Timorese."