Spot Runner, the start-up Web company that lets advertisers places ads on TV, has been sued by one of its investors, WPP Group for securities fraud and breach of contract, AdAge reports.

WPP, one of the largest world’s largest advertising agency companies, said Spot Runner’s executives aggressively promoted WPP’s investment in it to gain new investors, and then sold large quantities of their shares at growing valuations. It says Spot Runner did not disclose some stock sales, as required under an agreement.

The suit names Spot Runner CEO Nick Grouf and co-founder David Waxman, as well as investors including Pilot Group’s Bob Pittman, Index Ventures’ Danny Rimer and Battery Ventures’ Roger Lee. Peter Huie, Spot Runner’s general counsel is also named. WPP says the group sold their own secondary shares in the “pump and dump” scheme, and is seeking about $13 million in damages.

Complicating the relationship is that WPP apparently sought to sell its stock in the company too. “This lawsuit is about WPP, a minority shareholder, wanting to sell their Spot Runner stock retroactively,” the company said in an email statement. “This situation is unfortunate; we had hoped that we would have had a long relationship with WPP. We believe the claims are without merit and we will vigorously defend against them, including taking all necessary legal action to protect Spot Runner’s reputation.”

It’s not clear to what extent other factors are involved here, including possible tension between the two players as a result of Spot Runner’s business model. The company can be seen as a competitive force to WPP, because it lets advertisers go straight to Spot Runner’s online site in order to create and place ads on TV. It thus replaces services such as those provided by WPP. On the other hand, the company has struggled in the market place of late, and so it’s hard to argue that it’s a real threat to WPP right now.

WPP helped lead a $40 million investment into the Los Angeles company three years ago. WPP holds a 30 percent stake in the company, according to paidContent.

Spot Runner has gone through three rounds of layoffs lately, laying off more than 200 . It has raised a total of $111 million from WPP, UK media group Daily Mail, Grupo Televisa,, hedge fund Legg Mason Capital Management, French luxury group Groupe Arnault/LVMH, Allen & Company, Battery Ventures, Capital Research and Management, CBS, Index Ventures, The Interpublic Group and Tudor Investment Corporation.