Chinese officials convicted in President Xi Jinping's sprawling anti-corruption drive have embezzled or misused nearly $1 billion in public funds, a new report has found.

Official graft causes widespread public anger in China, and since taking over as the ruling Communist Party's leader in 2012 Xi has overseen a much-publicised campaign against the scourge.

But critics say there is a lack of transparency around the drive and that it has been used to settle political scores.

ChinaFile, a publication of the Asia Society in New York, has tallied nearly 1,500 publicly-announced targets of the campaign, and has released a searchable database.

It shows that 231 officials have been convicted and sentenced in Chinese courts -- only a fraction of those put under investigation by the Communist Party, which operates its own discipline system outside judicial supervision.

Chinese courts -- which are controlled by the party and have a conviction rate of more than 99.9 percent -- found that they embezzled or misused more than 6.3 billion yuan (nearly $1 billion), according to the verdicts against them, the database shows.

The documents included details such as one official spending 200,000 yuan of public funds on jade jewellery, and another attempting to hide a stolen 30 million yuan in his mistress' gardening company.

Xi pledged to target both high-ranking "tigers" and low-level "flies" in his drive.

But the database includes proportionately fewer fallen officials from President Xi's provincial power bases of Fujian and Zhejiang, which ChinaFile said "are among those that appear to have been treated more leniently".

David Zweig, professor of Chinese politics at the Hong Kong University of Science and Technology, told AFP on Friday: "If you're a Xi guy, you don't get purged, everybody else, it's open season.

"When he was in those places, he was able to move people into positions of authority. People who are allied to him, therefore there's no need to use the crackdown to transfer out people."