A top Chinese official once seen as a potential successor to president Xi Jinping has been sentenced to life in prison for taking more than $26m in bribes, according to state media.

Sun Zhengcai, a former politburo member and party boss of the southwestern city of Chongqing, is one of the highest officials to be toppled by an anti-graft campaign that critics say is Xi’s way to root out rivals rather than corruption.

Sun was given a “lenient” sentence in exchange for his cooperation, the court in the northern port city of Tianjin said on Tuesday. He was accused of taking advantage of his position to seek profits for himself and others. Sun pleaded guilty after a one-day trial in April.

The court said Sun had “gravely damaged the normal work order of national organisations and harmed the integrity of conduct by national employees”, according to a statement. The court said his “illegal gains” would be confiscated.

Sun, 54, was the youngest member of the ruling communist party’s 25-member politburo and was a rising star in the party. In 2012, he was sent to Chongqing to replace Bo Xilai, another top official who fell foul of Xi’s anti-corruption crusade. Chongqing, as one of China’s largest cities, is a key post for rising Chinese officials.

At one point, Sun was tipped to be elevated to the powerful politburo standing committee of seven people and helmed by Xi. Sun was seen by some as a candidate for leading the party in 2022.

Then last year, he became the first politburo member to be investigated since Bo, who was charged with corruption and sentenced to jail in 2013. Sun was expelled from the CCP in September after the party accused him of taking bribes and trading power for sex.

Last year, Sun, along with Bo, and China’s former security chief Zhou Yongkang, were named in an alleged plot to “usurp the party’s leadership and seize state power”. All three men have now been ousted from the party and jailed.

This year, China’s legislature amended the country’s constitution to abolish a two-term limit for the country’s president, giving Xi freedom to remain in power indefinitely.