The news comes as Belford and Roberts enter final talks with Abbott Mead Vickers BBDO about joining the agency. It is unclear how this will affect negotiations.
COI Communications triggered an investigation after it noticed that the executions for its UK Online paedophile awareness campaign submitted by O&M were radically different from those that ran.
Peter Buchanan, the COI deputy chief executive, said: "We immediately realised that there were significant differences. We contacted John Hegarty [the chairman of the Press jury] immediately."
The art direction for the UK Online campaign, by Belford, was altered before submission. The copy, by Roberts and Mark Fairbanks, was not changed.
For the Samaritans, one ad was submitted, titled "Big Ears", which was art directed by Belford and Paul Burch and written by Dave Williams, but it ran as a poster, not in the press.
Buchanan added: "It's a foolish thing for the creative team to have done. However, we are convinced that the senior management at O&M was unaware of this and this will not affect our long-term relationship."
Hegarty said: "It's essential we maintain the integrity of the awards for everyone's benefit. Without that they collapse into farce and ridicule. It is the responsibility of agencies to ensure the corrupt few don't damage the industry at large."
Mike Walsh, the European chairman of Ogilvy, said: "This agency does not cheat to win. I will not tolerate this behaviour or employ people who act in this manner."
Roberts, a member of the press jury, said: "A lot of agencies change ads a little. It was a minor visual tweak, we didn't think it would be a problem."
Belford added: "It's the same typeface, it's the same graphic style. We wanted to present it in the way we wanted it to appear."
The team's bonus scheme at O&M is linked to the amount of awards they win.
Now that O&M is stripped of the awards, Bartle Bogle Hegarty's campaign for Barnardo's takes the silver for best black-and-white press ad while Paradigm's "daughter" for The Samaritans takes the silver for best charity ad.
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