NDTV’s 194-page complaint was filed in a New York court in late July, but WPP says neither it nor any of it its operating companies have yet been served with what it refers to as “the hypothetical lawsuit”.

“In any event,” the company said in a statement this morning, “there is no merit whatsoever in any of the claims made in the hypothetical lawsuit relating to the WPP parties, nor do the courts of New York have any jurisdiction to hear such claims.”

WPP said it is in the process of issuing an immediate application to strike out the lawsuit and will be seeking to reclaim costs.

TAM, which is jointly owned by Nielsen, recently met with Indian advertising and media executives in the wake of the NDTV allegations to present a six-point action plan for tackling concerns about its ratings data.

WPP said: “TAM has taken and continues to take stringent measures to protect the panel against repeated attempts at tampering by currently unknown parties and has recently agreed a series of additional steps with the industry to remove any questions marks about the quality and reliability of the TAM data.”

Nielsen has yet to comment on the lawsuit.