We are all Alastair Campbells now. Spin doctors antennae whirred around this week when the volunteers who run Wikipedia discovered that staff of US senators and congressmen had been busy burnishing their bosses entries in the internet encyclopedia.

Millions of people turn to the reference site to look up facts - and change them. The non-profit making project to build an internet encyclopedia is the 19th most-visited site in the world. Three per cent of all webpages visited are Wikipedia pages. Its guiding, and democratic, principle: anyone can anonymously edit it. Increasingly, it seems, politicians and their staff are among the most dedicated editors.

Patrolling the 962,652 entries in the English Wiki - more than double the number a year ago - its idealistic volunteers found other examples of "politically motivated editing" emanating from Washington. In one case, an intern for Democratic representative Marty Meehan deleted a reference to his broken promise to only serve four terms. In another, the office of Senator Norm Coleman deleted an unflattering reference to voting with President George Bush 98% of the time in 2003, despite running as a moderate the year before. Wikipedia took draconian action: all computers connected to servers at the House of Representatives were temporarily denied access to the site.

Computers linked to Canada's House of Commons and the German Bundestag also fiddled with entries, according to Wikipedia. But Jimmy Wales, the Florida-based founder who was embarrassingly exposed for tweaking his own entry, said no suspicious activity had yet been recorded on the computers of Westminster and Whitehall.

Why do our slow-witted special advisers twiddle their thumbs while websavvy idealists write their bosses biographies? The Guardian could help. I bring up Tony Blair's entry. It appears a perfect example of a Wiki entry: accurate, informative, well-sourced and neutral in tone. But every choice of fact is a subjective act. And theres one our Tone wouldn't like: "Euan Blair received widespread publicity after police found him drunk and incapable." C'mon guys, the kids are off limits. Snip. I cut it out.

"While the Blairs have stated that they wish to shield their children from the media, they have not always been able, or willing ... " Hang on, "willing"? What does that imply? Cut. Save. Refresh page. Tony's Wiki entry is now a lot shinier.

Time to buff up the Guardian. The stereotypical Guardian reader is, Wikipedia explains, a lentil-munching, sandal-wearing lefty. "Like most stereotypes, to some extent this one is both inaccurate and outdated." Let's get rid of "to some extent", eh?

I add some positive spin about our rising circulation. Hang on, there is someone missing from the list of "notable regular contributors (past and present)". Ian Aitken, Julian Borger, Emma Brockes: excellent, excellent. But no "Patrick Barkham". I slip the name in. It looks nice, if suspiciously anomalous.

Ah, the sweet power of the spin doctor (tempered by the growing anxiety that a volunteer will hunt me down and attack me with worms or bots or turn my Mac into a zombie computer). Wikipedia records the internet protocol address of the computer on which every edit occurs. They could easily trace my edits to the Guardian. Its volunteers cleverly trapped the US spinners by sending emails to their offices. When they received replies, they found the IP addresses contained in the emails matched those of the dodgy editors.

Time to phone Wikipedia. Does the furore over the politicians gilding their own lilies undermine its credibility? "It's more damaging to the persons involved," says Mr Wales. "We were able to catch these bad edits very quickly and good edits were incorporated very quickly."

The site is still smarting from bad publicity about the biography of the US journalist John Seigenthaler, which incorrectly linked him to the Kennedy assassinations. The libellous allegations were not spotted for months before they were removed, leading to criticism about its reliability.

Mr Wales says the "whitewashing" editors from Washington are treated "just like editors from a grammar school. If they behave themselves, that's fine. If not, they get blocked."

What does Wikipedia rule on people adding gloss to their own entries? "It's not absolutely forbidden to edit an article you're involved in but it's not considered good practice," says a UK spokesman, David Gerard.

Marty Meehan recanted. "It was a waste of energy and an error in judgment on the part of my staff to have allowed any time to be spent on updating my Wikipedia entry," he said.

And so must I. Shamed by my crass attempts to subvert the democratic goal of a free encyclopedia on the internet, I return and remove my "bad edits" to leave the pages just as they were. Will the world's spin doctors suffer similar pangs of conscience?