The co-founder of Wikipedia Jimmy Wales has criticised Bell Pottinger's "ethical blindness" as the lobbying company admitted altering details of its clients' reputations online.

Bell Pottinger last night said that its digital team used a number of accounts to edit Wikipedia articles, although it stressed it had never done anything illegal.

Last night, Mr Wales told The Independent: "I am astonished at the ethical blindness of Bell Pottinger's reaction. That their strongest true response is they didn't break the law tells a lot about their view of the world, I'm afraid.

"The company committed the cardinal sin of a PR and lobbying company of having their own bad behaviour bring bad headlines to their clients, [and] did so in a fashion that brought no corresponding benefits.

He added: "There are ethical PR companies out there."

Evidence seen by The Independent and the Bureau of Investigative Journalism (BIJ) shows the company made hundreds of alterations to Wikipedia entries about its clients in the last year. Some of the changes added favourable comments while others removed negative content. Several Wikipedia accounts have been suspended pending an investigation by Mr Wales.

Among the changes made in the past year by a user – traced to a Bell Pottinger computer – who made the alterations under the pseudonym "Biggleswiki" were:

* Removal of the reference to the university drugs conviction of a businessman who was a client of Bell Pottinger;

* Edited material relating to the arrest of a man accused of commercial bribery;

* Editing of the entries for prostate cancer expert Professor Roger Kirby and his firm, The Prostate Centre. Both are clients of Bell Pottinger. The user added Mr Kirby into a separate page on "prostatectomy" as a notable expert, and edited the entry on the Lockerbie bomber Abdelbaset al-Megrahi to include comments made by Mr Kirby about Megrahi's cancer.

* Editing the articles of both Chime Communications, parent company of Bell Pottinger, and Naked Eye Research after the former company bought 55 per cent of the latter.

In other cases, damaging allegations against clients of Bell Pottinger, which The Independent cannot publish for legal reasons, were removed from Wikipedia. The connection was first spotted by the blogger Tim Ireland, after reading the joint investigation into Bell Pottinger by the BIJ and The Independent on Tuesday. Undercover BIJ reporters, posing as agents of the Uzbek government, were told that "sorting" negative coverage and criticism on Wikipedia was a service the company could provide.

One of the first changes made by "Biggleswiki" was to add a series of paragraphs advertising the lengths that a money-transfer company Dahabshiil went to comply with international regulations. After another user complained about edits being unduly positive, Biggleswiki responded: "I am trying to expand this article with plain, referenced facts about Dahabshiil (I can easily change any references that you're uneasy with). Your sole agenda seems to be to add a 'Controversy' section filled with as yet unproved allegations."

A spokesman for Dahabshiil said: "We have never heard of Biggleswiki, and know nothing about them. We are currently trying to get to the bottom of this." The personal Wikipedia page of "Biggleswiki" has been edited several dozen times. On one occasion, the user making the changes was not logged in; as a result, the change was attributed to the IP address "109.231.203.194". An IP-lookup search revealed that the IP address in question was identified as being linked to "BELL-POTTINGER-COMMUNICATIONS-NETID7353".

The Independent also contacted The Prostate Centre. A spokeswoman confirmed it had asked Bell Pottinger several times to make changes and add information to its Wikipedia entries.

James Thomlinson, head of digital at Bell Pottinger, admitted last night to The Independent: "Biggleswiki is one of a number of accounts that the digital team have used to edit Wikipedia articles. I would like to point out that while we have worked for a number of clients like The Prostate Centre, we have never done anything illegal. We have never added something that is a lie or hasn't been published elsewhere and we have never tried to 'astroturf', ie create fake positive reviews to sell a product. If we have been asked to include things about clients that are untrue we have always said no and pointed to Wikipedia's strict guidelines.

"We have also ensured that for every change that we have made we have sought the approval of the wider Wikipedia community first."

The backlash: Reaction online

Bell Pottinger's executives claimed they had mastered the internet, could manipulate Google searches and whitewash Wikipedia entries on behalf of clients who paid handsomely for the services.

But since revelations about the firm's "dark arts" and their influence at the heart of government were published by The Independent, Bell Pottinger has found that its own online profile has become less flattering.

On Google, 164 stories about the recordings made by undercover journalists from the Bureau for Investigative Journalism now crown Bell Pottinger's search results page.

A large chapter on Bell Pottinger's Wikipedia page has appeared under the heading "Criticism", which refers to the investigation and contains links to new stories about it. Padraig Reidy, from the Index on Censorship, said: "The web is still a very free place, whether autocratic governments or PR people working with autocratic governments try to control it."

Charlie Cooper