Martin Sorrell has beaten WPP in the race to buy the highly coveted Dutch agency MediaMonks, in a move that is set to further strain tensions with the company he founded.

The 73-year-old Sorrell left the world's biggest advertising group WPP in April over a complaint of personal misconduct. Leaving without a non-compete clause, he set up a new company weeks later and took on WPP in a bid battle for its first acquisition.

WPP warned Sorrell earlier this month that he could lose his multi-million pound share awards payout if he did not back off from the competition for MediaMonks.

"The merger (with MediaMonks) represents the first move by S4 Capital to create a new era, new media solution embracing data, content and technology, which meets client needs in an always-on environment," Sorrell's new venture, S4 Capital, said.

MediaMonks, with revenue of around 110 million euros, employs more than 750 people in 10 countries to support clients including Adidas, Amazon, Google, Netflix, Hyundai and GE.

The owners of the group will receive shares in S4 Capital as well as cash. They will not get an earn-out in a bid to encourage them to stay. S4 did not put a price on the deal.