The entry on Dolly the sheep was said to contain inaccuracies
The report, published in December last year, compared the accuracy of online offerings from Encyclopaedia Britannica and Wikipedia.
Nature found that both were about as accurate as each other on science.
Encyclopaedia Britannica has hit back at the findings, calling for the paper to be retracted.
In a document on its website, Encyclopaedia Britannica said that the Nature study contained "a pattern of sloppiness, indifference to basic scholarly standards, and flagrant errors so numerous they completely invalidated the results".
The scholarly slanging match prompted an equally robust response from Nature.
"We reject those accusations, and are confident our comparisons are fair," it said in a statement.
Nature said it did not intend to retract the original article.
Online collaboration
The original study was conducted by the Nature news team. They asked a number of scientists to assess 50 pairs of articles from relative newcomer Wikipedia and from the well established encyclopaedia.
Wikipedia was founded in 2001 and is based on wikis, open-source software which allows anyone to edit, add, delete, or replace an entry. It relies on volunteer contributors to update its pages.
Topics in the Nature study were as diverse as the Archimedes Principle and Dolly the sheep. The reviewers were asked to check for errors, but were not told about the source of the information.
The study found only eight serious errors, such as misinterpretations of important concepts, four from each encyclopaedia.
However, Nature also claimed to have found other factual errors: 162 in Wikipedia and 123 in Britannica.
Wikipedia criticisms
Although the longer established encyclopaedia does not claim to be error free, it said that the research "grossly exaggerated Britannica's inaccuracies" and that according to the figures "Britannica was far more accurate than Wikipedia".
In a lengthy document, it went on to rebut more than 50 specific points raised in the study.
Following the Nature study, both Wikipedia and the Britannica made corrections to some of their entries.
Late last year, Wikipedia came under fire for the accuracy of its articles.
In particular, prominent US journalist John Seigenthaler attacked an entry that incorrectly named him as a suspect in the assassinations of President John F Kennedy and his brother, Robert.
The false information was the work of Tennessean Brian Chase, who said he was trying to trick a co-worker.
Wikipedia responded to the criticisms by tightening up procedures.
1913 advertisement for the Britannica
''Encyclopædia Britannica'' has strongly criticised the scientific journal ''Nature'' for last year's investigation into the encyclopedia's accuracy compared to that of the open-source online encyclopedia, Wikipedia. ''Britannica'' also called for a retraction of the article. ''Nature'' has rejected the accusations, saying that their comparison was fair and that they do not intend to retract their report.

In a 20-page response (titled "Fatally Flawed") to the report's findings that there was not a significant difference in accuracy between the two encyclopædias, Britannica wrote that 'Almost everything about the journal's investigation ... was wrong and misleading.' The document goes on to call the investigation 'invalid', 'completely without merit' and 'careless'. Britannica also accused ''Nature'' of 'misrepresenting its own results'. The last 12 pages of this comprehensive rebuttal are responses to specific article criticisms, mainly consisting of differences of opinion on style and article composition, but some citing outright factual errors on ''Nature'''s part.

In their response, ''Nature'' refused to reveal their original data for comparison, and commented that ''Britannica'' had raised their grievances in private some time ago, and then received no further correspondence until ''Britannica'''s open letter of 22 March 2006. ''Nature'' notes that ''Britannica'' criticised 'less than half the points their reviewers raised', and states that the two encyclopædias were subject to the same treatment.

Wikipedia has been stigmatised as unreliable due to its open-source nature and a perceived problem with vandalism.  The December 2005 study was seen at the time as a major boost to the credibility of Wikipedia.  Jimmy Wales was notified by one of his team members, on 27 January 2006 that all corrections provided by ''Nature'' were in place.  Recent changes to some of the Wikipedia editing policies have attempted to resolve some of the reliability issues raised.

Wikipedia has yet to comment.