Wikipedia, the online encyclopaedia that relies on volunteers to write nearly four million articles, is about as accurate in covering scientific topics as the Encyclopaedia Britannica, the journal Nature has found.

The claim, based on a side-by-side, comparative peer review of articles covering a broad swath of the scientific spectrum, comes as Wikipedia faces criticism over the accuracy of some entries.

Two weeks ago John Seigenthaler, the founding editorial director of USA Today, revealed that a Wikipedia entry that ran for four months had incorrectly named him as a suspect in the assassinations of president John F. Kennedy and his brother Robert.

Such errors appear to be the exception rather than the rule, Nature said. Experts reviewing 42 articles found that the average scientific entry in Wikipedia contained four errors or omissions, while Britannica had three. Of eight "serious errors" the reviewers found – including misinterpretations of important concepts – four came from each source.

"We’re very pleased with the results and we’re hoping it will focus people’s attention on the overall level of our work, which is pretty good," said Jimmy Wales, who founded Wikipedia in 2001.

Mr Wales said the accuracy of his project varies by topic, with strong suits including pop culture and contemporary technology. Wikipedia’s stable of dedicated volunteers tend to have more collective expertise in such areas, he said. Mr Wales acknowledged that the site tends to lag when it comes to the arts, such as the winner of the Nobel Prize for literature for a particular year.

Next month, Wikipedia plans to start testing a new mechanism for reviewing the accuracy of its articles. The group is also working on ways to make its review process easier to use for people who have less familiarity with computers and the internet.

Encyclopaedia Britannica officials declined to comment on the findings, saying that they haven’t seen the data. But spokesman Tom Panelas said such comparisons, assuming they’re conducted correctly, are valuable "because they tell us things you wouldn’t know otherwise." He said Britannica researchers would review the Nature study and correct any errors discovered.

While some Britannica officials have publicly criticized Wikipedia’s quality in the past, Panelas praised the free service for having the speed and breadth to keep up on topics such as "extreme ironing." The sport, in which competitors iron clothing in remote locations, is not covered in Britannica.

Unlike Britannica, which charges for its content and pays a staff of experts to research and write its articles, Wikipedia gives away its content for free and allows anyone to submit and edit entries.

Wikipedia, which boasts 3.7 million articles in 200 languages, is the 37th most visited website on the internet, according to the research service Alexa.

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