Former UN Secretary-General Ban Ki-moon said he was giving up his plans to run for president of South Korea, national media quoted him as saying Wednesday.
He said he was "disappointed by old-fashioned, narrow-minded egoistic attitudes by some politicians, and I came to a conclusion that it would be meaningless to work together with them".
Politics in South Korea have been upended by a massive scandal that prompted millions to take to the streets in protest, the impeachment of the country's conservative president, Park Geun-hye, and a power handoff to the prime minister.
Prosecutors said Park, South Korea's first woman president, had a major role in the alleged corruption. "I'm sorry for disappointing many people".
Ban, 72, returned to South Korea on January 12 after serving 10 years as United Nations secretary-general.
If the Constitutional Court approves Park's impeachment, an election will be held within 60 days.
The media leapt on a series of minor blunders, for instance when he took the airport express train instead of a limo on his return to South Korea, but didn't know how to buy a ticket.
The media coverage and his family scandals have led to a fall in Ban's support rating to second place behind the presidential candidate of the main opposition Democratic Party - Moon Jae-in, after peaking at almost 30 per cent previous year.
Ban returned home last month after a decade in NY and was widely expected to run in elections due this year, but his putative candidacy ran into a series of stumbles.
Earlier this year, Ban's brother and nephew were charged by US prosecutors with participating in an worldwide bribery scheme over payments related to the sale of a skyscraper complex in Vietnam.
A poll by R&Search released on Wednesday showed Ban's support continuing to slip to 16.5 percent from 18 percent a week ago, compared to 35.2 percent for Moon, up from 34.8 percent a week ago.
Ban served for two years as South Korea's foreign minister before leading the United Nations for a decade.