Wikipedia, the free online encyclopaedia that anyone can edit, has countered claims that it is losing participants, but has admitted that it needs to do more to attract contributors.

Wikipedia is the fifth most popular web property in the world, logging 344 million unique visitors last month, according to figures from comScore Media Metrix.

However, a report in The Wall Street Journal this week claimed that the site is losing huge numbers of the 'editors' who write the topic entries.

The report said that Wikipedia had lost 49,000 editors in the first three months of 2009, a full 10 times as many as it did in the first three months of 2008, when it lost 4,900 editors.

The newspaper then went on to speculate about the reasons for the wholesale desertions, suggesting that editors often feel exasperated when asked to debate the content of articles time and time again.

However, Wikipedia has claimed that the numbers quoted in the report are not accurate because they are taken from research that measures when an individual Wikipedia editor starts editing and when they stop.

"It is impossible to make a determination that a person has left and will never edit again. There are methodological challenges with determining the long-term trend of joining and leaving," said the company in a blog post.

"Studying the number of actual participants in a given month shows that Wikipedia participation as a whole has declined slightly from its peak two and a half years ago, and has remained stable since then.

"The number of articles in Wikipedia keeps growing. There are about 14.4 million articles in Wikipedia, with thousands of new ones added every day."

The company explained that it now has a "usability initiative", which aims to make it easier to contribute to Wikipedia and its sister projects by improving the underlying open-source technology, and an "outreach initiative" that will help recruit new volunteers.

"Removing barriers is key to recruiting new editors," Wikipedia said.