Around 22% of WPP investors failed to back the £43m pay package of its chief executive Martin Sorrell at the company's annual meeting today, in the latest showdown over the high-profile boss's remuneration.
The event has sparked several clashes between investors and Sorrell, one of Britain's most well known company bosses.
In 2012 nearly 60% did not back the chief executive's pay deal.
Meanwhile, WPP, which is the world's biggest advertising company, said it posted a slight slowdown in sales growth in the first four months of the year due to weaker trading from some parts of the business in April.
The firm said that like-for-like net sales up were up 2.3% in the period compared with first-quarter growth of 2.5%.
"The pattern of net sales growth in 2015 is generally the same as the final quarter of 2014 and first quarter of 2015 ,with April marginally softer, as parts of the group's advertising, data investment management and branding and identity businesses were slightly slower," it said.
As in the first quarter, WPP, which counts the likes of Ford, Unilever and Microsoft among its clients, saw like-for-like revenue growth in all regions and business sectors, except data investment management.
Growth was particularly strong in the UK and Asia Pacific, it added.