The group’s operating profit rose 25.8% to £1.1bn, with revenue up 32.3% to £7bn. Its operating profit margin was 15.5%, which represented a decline of one percentage point.
Kingston Smith said that only a small part of Publicis Groupe’s revenue growth was organic and attributed most of it to the acquisition of Sapient.
Havas had the second-strongest growth after embarking on an acquisition spree in 2015.
The French holding company reported operating profit of £229m in 2015, a rise of 19.8%, and revenue of £1.6bn, up 17.3% year on year. Its operating profit margin was 14.4%.
Kingston Smith ascribed much of Havas’ growth to the 13 acquisitions it made during 2015, including Fullsix, a European digital communications company. Excluding acquisitions, the holding company’s organic revenue increased 5.1%.
Interpublic, which owns McCann Worldgroup, had the third-highest growth in operating profit, rising 10.6% to £570m. Its revenue grew 1% to £5bn.
Although Kingston Smith said that 2015 was another consistent year for IPG, with the lowest operating profit margin in the market at 11.5%, it added that the group still has "room for improvement".
Dentsu Aegis Network reported results for the nine months to December 2015 after changing its year-end to align with Aegis Group, the UK business it acquired in 2013.
If Dentsu Aegis’ figures for the nine months are extrapolated across the full year, the owner of Mcgarrybowen and Carat increased its operating profit by 8.1% year on year to £767m and its revenue by 31.9% to £4.8bn.
WPP remains the largest holding company by profit and revenue. Its operating profit rose 8.3% year on year to £1.6bn in 2015, while revenue increased 4.6% to £10.5bn. The group’s operating profit margin grew by half-a-percentage-point to 15.5%.
Omnicom, the second-largest holding company, saw operating profit drop 1.2% to £1.3bn. Revenue also declined by 1.2% to £9.9bn. Operating profit margin remained static at 12.7%.