
A senior reporter for the Shizuoka Shimbun used information from the Japanese edition of the online encyclopaedia in a story about former Japanese prime minister Kiichi Miyazawa, who died on 28 June.
The journalist told how Miyazawa had once ordered former Soviet foreign minister Andrei Gomyko to sit down during heated negotiations over the disputed Kuril Islands in the 1970s.
Japanese bloggers and other internet users quickly noticed a strong similarity between the wording of the reporter's account and the page about Miyazawa on the Japanese edition of Wikipedia.
The newspaper apologised to readers this morning for not revealing the source of the information, the Mainichi Daily News reported. A senior editorial executive described the reporter's actions as "inappropriate".
The reporter claimed that he did not name the source because he believed the information to be common knowledge, the report said.
The Wikipedia page cites a newspaper in northern Japan as the source of its information. The original story actually appears to be anecdotal and has no named sources.
Wikipedia is one of the most popular websites on the internet, but it regularly faces criticism for inaccuracy.
Co-founder Larry Sanger, who left the project in 2002, described Wikipedia earlier this year as "broken beyond repair" and "frequently unreliable", although he conceded that it was "often quite useful".
The Shizuoka Shimbun is a regional daily published in the Shizuoka area. It has an average daily circulation of around 750,000.