Diamond company DeBeers has pulled its $47m (31m) US account out of NW Ayer & Partners after 57 years and consolidated it into J Walter Thompson.
JWT already handles the account in the rest of the world.
A statement from DeBeers points to advantages in having the services of a single multi-national agency with global resources on the account.
The move is a significant blow to NW Ayer which has been embroiled in a management dispute in recent months. It is still reeling from the sudden departure of its chairman and chief executive Steve Dworin in June.
Dworin is understood to have left after becoming frustrated with Richard Humphreys, president of NW Ayer’s holding company Adcom, and WY Choi who owns 99 per cent of Adcom.
Dworin favoured a plan for key NW Ayer executives to receive a 25 per cent equity stake in the agency, but this failed to come to fruition.
There are also increasingly strong rumours of a split between Humphreys and Choi. Reports suggest Humphreys may make a bid for NW Ayer.
NW Ayer ran a long-standing campaign for the company with the strapline, “A Diamond is Forever”. The line is likely to be retained as its worldwide theme.
DeBeers spent $47m on advertising in the US last year but Ayer claims spend for next year is expected to be $35m (23m).