Veteran lawmaker Masajuro Shiokawa, replaced as finance minister in Monday's Cabinet reshuffle, said Thursday he will not run in the next House of Representatives election, expected to be held in November.
"I'll retire from the political arena on resigning as finance minister," Shiokawa, 81, told colleagues within the Liberal Democratic Party during a meeting.
Shiokawa, a supporter of Koizumi's fiscal reform drive, had hinted at retirement earlier in the week, having been hospitalized for two weeks with an inflamed gallbladder.
After Koizumi handed him the finance portfolio in April 2001, Shiokawa quickly became recognizable among the public, earning the nickname "Shiojii" ("Grandpa Shio").
As finance minister, Shiokawa worked to cut the nation's huge public debt, initially keeping new government bond issues below 30 trillion yen, as pledged by Koizumi.
But the ailing economy eventually forced Koizumi to abandon this pledge, with the Finance Ministry planning to issue 36.45 trillion yen in fresh bonds in the current fiscal year.
Shiokawa at times provoked confusion through his verbal gaffes. He sparked a surge in the yen in July 2002 when he alluded to a specific exchange-rate level, a rare move by a finance minister.
Shiokawa kicked off his political career in 1964 as deputy mayor of Fuse, a town later incorporated into the city of Higashi-Osaka, at the age of 36.
First elected to the House of Representatives three years later, Shiokawa has won 11 Lower House terms.