Detained artist Ai Weiwei was accused of plagiarism in state media last night and described as a 'third-grade' artist who only protested to seek media attention.
It was the first direct offensive against Ai in an article released by Xinhua, although Global Times, an English newspaper under People's Daily, ran two pieces against him last week, in a move widely seen as an attempt to build a legal case against the outspoken artist.
Ai has not been seen since last Sunday, when police stopped him from boarding a flight from Beijing to Hong Kong.
The Xinhua article referred to various accusations against Ai that had surfaced on the internet within hours of an investigation into his activities being announced. One said Ai stole an art professor's idea by using 1,001 ordinary Chinese as part of a 'living exhibit' in a show in Germany in 2007.
Other online postings accused Ai of dodging income taxes and monopolising funds and resources in the art world, among other things.
'None of the claims, however, have been independently investigated,' Xinhua said.
It also quoted anonymous 'participants in Chinese artistic circles' as 'evaluating Ai's achievements as third rate' and describing him as an 'amateur artist'.
And it quoted people who challenged Ai's sincerity in his protests, saying he only took part as an onlooker and put others in danger.
'Ai's criticism of the government became increasingly open and magnified in the past two years due to his increasing exposure to the media,' the Xinhua piece said.
It did not mention the start of Ai's activism - when he began an independent count of the death toll of the Sichuan earthquake in 2008.
The article, which was only released in English, did not give details of the possible charges resulting from the police investigation.
On Wednesday the agency said Ai was being investigated for economic crimes, but it gave no details.