The move follows the company’s announcement in July that it would be reviewing its Buy segment, which provides data on consumers’ purchase behaviour.

Revenue from the segment in the second quarter of 2018 decreased 4.1% to $789m, or 5.4% on a constant currency basis, compared to Q2 2017.

The decision to expand the strategic review has been taken by the company’s board of directors after consultation with Nielsen’s management and financial and legal advisers.

A broad range of options will be assessed as part of the review, including continuing to operate as a public, independent company, separating out either the Buy or Watch segments, or a sale. No timescale has been set for completion of the review.

The company’s advisers on the review are J.P. Morgan Securities, Guggenheim Securities, and Wachtell, Lipton, Rosen & Katz.

In August, investment management company Elliott Management disclosed that it owns an 8.4% stake in Nielsen and said it would encourage the company to explore a sale.

James Attwood, executive chairman of the board (pictured), said: "The board continues to support the company’s strategic priorities, including Total Audience, the Connected System and our operational transformation, including cost out initiatives and consolidations designed to increase agility. However, the board believes that a broad review of strategic alternatives is in the best interest of the company and its shareholders.

"As the board conducts its review, we and our valued associates remain focused on providing clients with the most complete understanding of what consumers watch and buy with mission critical data that enables markets around the world to act faster, more efficiently and with greater confidence."