The Chinese mainland ranked 80th in Transparency International's (TI) corruption perceptions index published on Wednesday, slipping from 75th last year.
Experts agreed the situation has become more serious in China, but many expressed optimism in the new leadership, which has shown resolve in changing the ruling Party's image since the major power transition in November.
The Chinese mainland's ranking is far below the Hong Kong Special Administrative Region, which is 14th, and Taiwan, which is at 37, according to the Berlin-based group, which made the list based on perceptions from institutions.
Ren Jianming, vice-president of TI-China and also a professor at Tsinghua University, said that the slip reflected the serious and emerging need in China to combat corruption.
However, it does not make much sense to compare one country or region with another, as the purpose of publishing this rank is to make the public and authorities reflect on what they have done in the last year, Ren told the Global Times.
Speaking about China's fall in the rankings, Ren said some widely reported cases such as Chongqing's former Party chief Bo Xilai being removed from his post for corruption and breaching discipline might have affected the result, as many who were surveyed would think Bo's case represented the whole situation in China.
"The facts could show the opposite, in which the government could have intensified anti-corruption efforts and more cases were reported," Ren added.
According to the Party's disciplinary body, more than 600,000 Party officials have been investigated for corruption-related activities since 2007, and 200,000 of them were transferred to judicial organs for prosecution.
Gan Chaoying, professor of law at Peking University, said although more corruption cases had been exposed, she felt optimistic so far about the newly-elected Party leaders.
Gan said the Party has made the first step in combating corruption through Xi's pledge to promote the Constitution and the rule of law.
"To fight corruption, the next step is to disclose officials' assets. It's an unavoidable trend," Gan told the Global Times.