A South Korean appeal court on Friday extended ex-president Park Geun-hye's prison sentence for corruption and abuse of power by one year.
The decision by the Seoul High Court means the former head of state, who was ousted after a sprawling corruption scandal triggered mass protests, faces 25 years in jail.
Park was convicted in May of receiving or demanding more than $20 million from conglomerates, sharing secret state documents, "blacklisting" artists critical of her policies, and firing officials who resisted her abuses of power.
Her 10-month trial highlighted shady links between big business and politics in South Korea, with Park and her close friend Choi Soon-sil accused of taking bribes from corporate bigwigs in exchange for preferential treatment.
At the time she was given a 24-year sentence but the prosecution appealed, seeking a 30-year term.
South Korea's high court said Friday that Park had collaborated with Choi to "demand money and other business favours" and browbeat firms into hiring Choi's friends.
"She also forced senior executives at private companies to step down, seriously abusing her power as president, bestowed upon her by the people, to seriously violate freedom of entrepreneurial activities."
It upheld the original verdict, adding: "The court... sentences the accused to 25 years in prison and imposes a fine of 20 billion won ($18 million)."
Park -- who did not appeal against her conviction -- has been boycotting the court, accusing the judicial process of being politically motivated, and was not present to hear the ruling.
She has also been given eight more years for a separate conviction on charges including illegally receiving funds from the country's spy agency.
The penalties apply consecutively, meaning that unless Park has her sentence commuted the 66-year-old will be approaching 100 by the time she is due for release.
Park's conviction completed a dramatic fall from grace for the country's first female leader, the daughter of a former dictator who grew up in the presidential palace only to have both her parents assassinated and later become a figure of public fury and ridicule.
She is the third former South Korean leader to be convicted on criminal charges after leaving office, joining Chun Doo-hwan and Roh Tae-woo, who were both found guilty of treason and corruption in the 1990s.
In addition former president Roh Moo-hyun committed suicide in 2009 after being questioned over graft allegations involving his family.