The two consumer goods firms are hoping that the service will provide them with a more accurate picture of how many people see their ads across both TV and online platforms.

Agencies are also participating in the trials, including Omnicom Media Group, Aegis and Universal McCann.

Aegis Media’s chief research officer Mark Greenstreet said: “We’ve now entered an era where being able to measure and plan exposure to communications across all screen devices is essential in order to deliver efficient and effective display campaigns.”

Cross-platform ratings combine Nielsen’s online campaign ratings (OCR) data with TV audience data from Barb, the Broadcasters Audience Research Board.

OCR was launched in the US in August 2011 and in the UK a year later. It allows advertisers to measure whether their online ad campaigns reached their intended audiences. It combines Nielsen’s panels with aggregated, anonymous demographic data from participating online data providers.

Cross-platform ratings were first trialled in the US in March last year.