The impact of account losses such as Argos in the UK and Volkswagen in the US are likely to result in a sharp downturn in growth for the world's sixth-largest communications group during the final quarter.
Even now, Havas, the parent company of Euro RSCG Worldwide, Arnold and Media Planning Group, has one of the lowest growth rates in the sector.
In the UK, the group's business remained flat, with a good performance from mainstream advertising business offset by disappointing figures from its media and healthcare operations.
Industry commentators said that although the group's performance was an improvement on the beginning of the year, the market would not be pleased by predictions of a downturn.
Havas' recent revenue rise has been driven by growth in the US, with new assignments from RadioShack and Hershey. However, the group continues to feel the loss of its Intel business, while losing out to larger rivals through its lack of global scale.