A sex scandal has claimed the job of the man who has overseen China’s economic boom for the past four years.

Jin Renqing, the Finance Minister, has been forced to step down after having an affair with the mistress of another senior Communist Party official.

Mr Jin’s dismissal reflects growing concern in the Communist Party about the behaviour of senior party members.

The decision was taken as the party prepares for its five-yearly congress in October, when President Hu Jintao will anoint the next generation of leaders.

Although officials have refused to confirm his departure, Mr Jin is believed to have been demoted to a position in a government think-tank, suggesting that he did not commit a criminal offence.

Such a move would support reports that he kept a mistress, an increasingly common practice in China, for which several senior officials have been demoted.

Speculation has been intense that the 63-year-old ran into trouble as officers from the Central Commission for Discipline Inspection, the watchdog of party probity, investigated a corruption case involving Du Shicheng, a former party secretary of the port of Qingdao.

A report in the South China Morning Post indicated that a young society woman had affairs with Mr Du and Mr Jin. Mr Du was sacked from governmental and party posts last December for “serious breaches of discipline”, the party euphemism for corruption and moral lapses such as the keeping of a mistress.

The young woman who was involved with Mr Du was detained as part of the investigation into the party official and apparently confessed to intimate relationships with several senior officials. Some had abused their power to help to advance her business dealings.

Mr Jin would be the most senior official to lose his job since Qiu Xiaohua, the head of the National Bureau of Statistics, was dismissed in October amid reports that he had kept at least one mistress and even accepted a home in Shanghai from a wealthy businessman. He has been charged with bigamy.

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