Wikipedia has suspended at least 10 accounts linked to the public relations firm Bell Pottinger as it investigates allegations of content manipulation.
The online encyclopaedia's founder Jimmy Wales told the BBC the lobbyists had "embarrassed their clients".
He said a team of volunteers was looking at possible breaches of conflict of interest guidelines.
Bell Pottinger admitted to editing entries, but said it had "never done anything illegal".
Mr Wales said he was "highly critical of their ethics".
"I've never seen a case like this. In general when I speak to PR firms they have ethical guidelines that would prevent this kind of conduct."
While anyone is free to edit the encyclopaedia, the site's guidelines urge users to steer clear of topics in which they have a personal or business interest.
"I offered to pop by their office next week give them a speech on ethical editing of Wikipedia - but I guess they didn't think that was too amusing so they didn't respond," Mr Wales said....read more