Simon Birmingham announces shock retirement from politics

He also named China's more than $20 billion of trade strikes on Australia when he was trade minister, and the closing of borders during the global pandemic, as other key moments.

He also said he was proud of his "small role" in achieving marriage equality in Australia as to be the first Coalition frontbencher to support it.

He also said the country needed to learn the lessons from marriage equality in striving towards reconciliation with Aboriginal and Torres Strait Islander Australians, saying "we should strive to make make Australians proud of having the oldest continuous living culture in the world — not ashamed due to disadvantage, nor resentful due to perceptions of special treatment".

He also took aim at the "harder edges of the left and right who seek to divide our country", adding that "little is gained by culture wars, politicians obsessing over what happens in private bedrooms or anyone seeking to override evidence-based medical practice".

Birmingham also said the global rise of "populism and divisive tribalism" troubled him and risks Australia's social cohesion and economy.

A number of senior figures in the Lower House — including Opposition leader Peter Dutton and former deputy prime minister Michael McCormack — and many Liberal staffers were present in the Senate for Birmingham’s speech.

What they said: “It's always better to go when there's some wishing you to stay. And none of us is irreplaceable,” Birmingham said.

“Now is the right time for me, for my family, and for new career pathways. I'm excited that next year I will step into a new commercially orientated direction. You can be relieved to know it has nothing to do with lobbying, government relations, or commentary.

“This year I hit the big 50. It provided pause for gratitude on the wonderful time I've been fortunate to craft and reflection on the priorities that lie ahead. There's so much in my life I do have reason to be thankful for.

“John Howard was always generous with his time and advice. Tony Abbott gave me the opportunity of serving on the frontbench, and in the ministry.”

“Malcolm Turnbull promoted me to cabinet, backed me in the pursuit of difficult reforms, and brought me into this leadership group. And Scott Morrison was to challenge me with roles in the expenditure review committee, the national security committee, and the joys of being a campaign spokesperson through two elections.

“Politics should never be about the titles you have, but what you do with them. I hope to be judged to have left a positive legacy.

“My biggest fight as education minister was of course over school funding. I inherited a wicked dilemma. On one side, reforms recommended to the Gillard government by the Gonski review, which had been compromised by a big spending, no losers approach that instead of Gonski funding maintained 28 different funding deals for schools.

“On the other side were budget repair initiatives of the Tony Abbott government, that sought to strip away the big spending but had no chance of passing the Senate and also maintained funding inequities.

“After many conversations with the ever thoughtful David Gonski and the backing of Malcolm Turnbull, we determined the only way out of the dilemma was a principled implementation of the Gonski recommendations. Applying the principles meant having the courage to create losers as well as winners.

“Some fought hard, others played politics. That was their right, even if at times their positions betrayed their purported values. As I said at the time to some controversy, there was an opponent or two who sold out their values for a few pieces of silver. But many education leaders, faith leaders and experts put principles first.”