UPDATED 4.45PM THURSDAY (AEDT)

Coalition Senate leader Simon Birmingham has announced his retirement from politics, saying he “will step into a new commercially orientated direction” in 2025.

“You can be relieved to know it has nothing to do with lobbying, government relations, or commentary,” the opposition foreign spokesman said in his valedictory speech on Thursday afternoon.

“I will leave here just short of 18 remarkable years as a senator for the great state of South Australia,” Birmingham told the Senate.

“Perhaps it is best to get out before hitting 18 and reaching Senate adulthood, whatever that may look like.”

The South Australian senator entered parliament in 2007 and held the trade, finance and education portfolios in previous Coalition governments under Malcolm Turnbull and Scott Morrison.

Before Birmingham’s official announcement on Thursday, Opposition Leader Peter Dutton thanked him at the end of Question Time.

“Birmo has a young family and I know he’s going to look forward to spending more time with them, and he’s given an enormous amount to our country,” he said.

Prime Minister Anthony Albanese said the Liberal senator had “very broad respect right across the parliament, and he certainly has my personal respect”.

“He’s someone who is someone of integrity, who is easy to deal with and to get things done,” he said.

“To Simon and Courtney and their family, it is understandable that he’s made this decision, but I wish him all the very best.”

-with AAP