Daniel Brandt, a longtime critic of the Wikipedia online encyclopedia, says his analysis shows the site is rife with plagiarism.
Brandt said he found 142 instances of Wikipedia copy lifted from other sources after studying the site with a software program that picks up matches with other material anywhere on the Google search engine.
Wikipedia is an online encyclopedia that allows thousands of volunteer users to post, edit and delete items.
'They go around claiming it's almost as good as Britannica. They are trying to be mainstream respectable.' -Wikipedia critic Daniel Brandt
The site's administrators said they have reviewed the instances of plagiarism, many of them in biographical entries, and removed some as a result of Brandt's complaints.
Others contain material already in the public domain and will remain as is, they said.
Brandt, who operates a site called Wikipedia Watch, said Wikipedia should be held to a higher standard.
"They present it as an encyclopedia," Brandt said on Friday after announcing the extent of the plagiarism publicly.
"They go around claiming it's almost as good as Britannica. They are trying to be mainstream respectable."
Brandt said he used software to compare Wikipedia passages that were substantially similar to, and in some cases verbatim copies of, other published sites. He said he eliminated instances where other sites had copied from Wikipedia.
Criticism exaggerated, site claims
The site's founder, Jimmy Wales, acknowledged that plagiarized passages occasionally slip in but dismissed Brandt's findings as exaggerated.
Brandt has been a virulent critic of the site since an unflattering biography of him appeared on it, Wales said.
Wikipedia administrators investigate all claims of plagiarism and will review all postings by authors who are found to have plagiarized, he said.
Plagiarism is always possible in a site that offers "wide-open editing â¦ but in general we take a very strong anti-plagiarism stance," he said.