Nature magazine has some tough questions to answer after it let its Wikipedia fetish get the better of its responsibilities to reporting science. The Encyclopedia Britannica has published a devastating response to Nature's December comparison of Wikipedia and Britannica, and accuses the journal of misrepresenting its own evidence.

Where the evidence didn't fit, says Britannica, Nature's news team just made it up. Britannica has called on the journal to repudiate the report, which was put together by its news team.

Independent experts were sent 50 unattributed articles from both Wikipedia and Britannica, and the journal claimed that Britannica turned up 123 "errors" to Wikipedia's 162.

But Nature sent only misleading fragments of some Britannica articles to the reviewers, sent extracts of the children's version and Britannica's "book of the year" to others, and in one case, simply stitched together bits from different articles and inserted its own material, passing it off as a single Britannica entry.

Nice "Mash-Up" - but bad science.

"Almost everything about the journal's investigation, from the criteria for identifying inaccuracies to the discrepancy between the article text and its headline, was wrong and misleading," says Britannica.

"Dozens of inaccuracies attributed to the Britannica were not inaccuracies at all, and a number of the articles Nature examined were not even in the Encyclopedia Britannica. The study was so poorly carried out and its findings so error-laden that it was completely without merit."

In one case, for example. Nature's peer reviewer was sent only the 350 word introduction to a 6,000 word Britannica article on lipids - which was criticized for containing omissions.

A pattern also emerges which raises questions about the choice of the domain experts picked by Nature's journalists.

Several got their facts wrong, and in many other cases, simply offered differences of opinion.

"Dozens of the so-called inaccuracies they attributed to us were nothing of the kind; they were the result of reviewers expressing opinions that differed from ours about what should be included in an encyclopedia article. In these cases Britannica's coverage was actually sound."

Nature only published a summary of the errors its experts found some time after the initial story, and has yet to disclose all the reviewer's notes.

So how could a respected science publication make such a grave series of errors?