BEIJING: Last weekend a mid-ranking police officer in Shenzhen named Liu Shengqiang invited 1100 guests to a five-star hotel for his daughter's wedding banquet. The 500,000 yuan ($80,000) price tag was probably more than a few years' salary, although he did make 36,000 yuan from ''red envelopes'' - cash gifts from guests.

''I played low-profile, without inviting any leaders from the bureau,'' he told Southern Metropolis Daily. ''If you were in my position, you would understand. We have a lot of neighbours.''

His plea for empathy did not go unheeded. Chinese officials can indeed be bound in complex webs of social and official obligations. They are often expected to throw extravagant banquets and finance them by blurring official and ''grey'' income on the side.

''Don't panic! It's common in Shenzhen to spend hundreds of thousands on weddings,'' wrote one netizen. ''Here if you don't have assets of more than 10 million you are considered a have-not.'' The reason Mr Liu's banquet drew any attention at all was that just one week earlier a deputy police chief had been fired in the same city for almost exactly the same offence: throwing a housewarming party for 1000 guests and accepting money.

The line between ordinary business and corruption in China can seem rather arbitrary. A Horizon Research Consultancy survey of 1350 people in Chinese cities said this week found that corruption ranked as the single worst blot on China's international image, for the third year running.

And the Communist Party knows it has a problem, judging by the rolling campaigns of the past three weeks. At the end of last year Xinhua reported that the President, Hu Jintao, had convened a Politburo meeting to chart this year's corruption fight and display the party's ''superior morality'', while the National Audit Office said 251 billion yuan had been embezzled or misused in the first 11 months of last year.

On Thursday the Central Commission for Discipline Inspection - an opaque non-judicial party body that deals with corruption inside the party - said it was conducting a blitz against bribery and the siphoning of income at state-owned enterprises. The previous day the state media loudly publicised a report showing how many senior officials and executives had been caught with their hands in the till, and worse, and detailed the harsh punishments they received.

Another report said more than 2000 party cadres had been punished for corruption last year. One of the biggest scalps was Kang Rixin, fired as head of China National Nuclear Corporation, whose sprawling commercial and regulatory empire was responsible for the entire civilian and military nuclear production chain. It was noteworthy that Mr Kang was also a member of the standing committee of the Discipline Inspection body that detained him.

Corruption is not confined, of course, to the top of China's rapidly expanding nuclear system. In 2007 a village chief in Hunan province showed the Herald a bag of uranium ore that he had illegally dug from an abandoned mine, and said he needed millions of yuan to bribe local county officials in order to restart his smuggling enterprise.

Corruption in China is impossible to quantify. But despite the repeated crackdowns and publicity the problem appears to be growing at least as fast as the economy.

Transparency International's 2009 Corruption Perception Index ranked China 79th of 180 countries, worse than the previous year (72nd) and far worse than its 57th place in 2001.

''The fact is the situation of anti-corruption is 'still severe' after 30 years,'' wrote Xin Yu last month in Yanghuang Chunqiu, a bold political magazine.

Many observers say corruption is so thoroughly embedded in the party's system of control and loyalty that it is impossible for politically instigated campaigns to be effective.

Indeed, some say the three most prominent cases at the end of last year had a collateral benefit of chipping away at the political and financial bastions of Mr Hu's predecessor as president and chief political rival, Jiang Zemin.

The single biggest scalp in recent years has been Chen Liangyu, a Politburo member who was a Jiang protege.

Most independent observers say there is a strong link between corruption and the party's restrictions on internet and media freedoms and, particularly, stonewalling on judicial and democratic reforms since the Tiananmen Square crackdowns of 1989.

''Without reasonable division of power, frauds will keep taking place,'' Xin wrote.