Two former Ogilvy and Mather executives accused of defrauding the US government have been named by an ex-colleague as instigators of the scheme.

Onetime O&M staffer Peter Christanopoulos was giving evidence at the New York trial of two former senior partners at the agency, Shona Siefert and Thomas Early. Prosecutors say the pair conspired to overbill the $1 billion (€78m, £53m) Office of National Drug Control Policy account in 1999.

The prosecution alleges Siefert and Early undertook the faking and revising of time-sheets to make up a $3 million revenue shortfall in response to North America co-president Bill Gray's ire at the loss of income.

Chrisanthopoulos, O&M's national broadcast director at the time of the alleged conspiracy, told the court he was summoned to a meeting with Early and senior executive Ray Simko.

Chrisanthopoulos says he never doubted what Early wanted from him: to falsely inflate his timesheets, and those of his staff on ONDCP, "irrespective of the amount of work we actually did".

A few days later, Chrisanthopoulos says, he bumped into Seifert, the former executive group director on ONDCP and she told him he was getting new "targets" for that account, meaning the percentage of hours he logged on his timesheets, and that it was "very important for me [Chrisanthopoulos] and everybody else to use them".

Seifert's message was clear, Chrisanthopoulos said: that he should adopt bogus hourly percentages on timesheets "irrespective of the number of hours we actually worked".

Defense lawyers countered Chrisanthopoulos's testimony by pointing out he had apparently changed his story during the time of the government's investigation.

They also repeatedly reminded the jury that he hoped to avoid jail by cooperating with the prosecution.

Data sourced from AdWeek (USA); additional content by WARC staff