BEIJING, June 18 (Reuters) - China officially appointed its fifth-ranked leader Cai Qi as head of the Communist Party's central ‌ideology school, cementing his position as one of President ‌Xi Jinping's closest and most trusted confidants.

Cai became part of the party's seven-man Politburo ​Standing Committee, China's pinnacle of political power overseen by Xi, in 2022. Cai is also director of the party's General Office, making him Xi's de facto chief of staff.

China's two most recent leaders, ‌Xi and Hu Jintao, ⁠had both served as head of the elite Central Party School before ascending to the top leadership ⁠position.

By taking the helm of the top party school, Cai, 70, unites the party's organisational, doctrinal and administrative apparatus under a single Standing ​Committee member — ​a rare concentration of power.

Cai ​replaced Chen Xi, 72, as ‌the new president of the National Academy of Governance, the human resources ministry announced on Thursday.

Established in 1994, the academy has operated jointly with the Central Party School since 2018 as one institution under party leadership and is responsible for training senior Chinese ‌officials and shaping party ideology.

Thursday's official statement ​follows a state media report earlier ​this month noting that ​Cai attended a spring semester graduation ceremony of the ‌school and academy as president.

Cai ​has longstanding ties ​with Xi through overlapping careers in the provinces of Fujian and Zhejiang.

In 2017, Cai became part of the then 25-member ​Politburo, the party's second-highest ‌decision-making body, as Xi started his second term as ​leader of the Communist Party.

(Reporting by Beijing Newsroom; editing ​by Philippa Fletcher and Alex Richardson)