A judge on Friday cited strengths of a suit charging Silicon Valley giants with secretly agreeing not to "poach" each other's workers but shot down a request for broad class action status.

US District Court Judge Lucy Koh reasoned that plaintiffs in a lawsuit filed against Apple, Google, Intel, Intuit, Adobe, Lucasfilm and Pixar had evidence of antitrust violations but sought to represent too broad a collection of workers.

"The court is most concerned about whether the evidence will be able to show that the defendants maintained such rigid compensation structures that a suppression of wages to some employees would have affected all or nearly all class members," Koh said in a 53-page ruling.

"The court is also concerned that plaintiffs' proposed classes may be defined so broadly as to include large numbers of people who were not necessarily harmed by defendants' allegedly unlawful conduct."

The judge left the door open for attorneys to renew their request for class action status, but with the group narrowed.

The original request asked for the named plaintiffs in the case to represent anyone who was employed by one or more of the accused companies on a salaried basis during about a four year period ending in 2009.

The broader the class in a civil lawsuit, the higher the potential payout in event damages are awarded.

During a January hearing in her courtroom in the California city of San Jose, Koh referred repeatedly to email evidence that included a request in 2007 by then Apple chief Steve Jobs that Google stop recruiting Apple workers.

Koh early this year cleared the way for Apple chief Tim Cook, Google chairman Eric Schmidt and Intel head Paul Otellini to face questioning in the "no-poaching" lawsuit.

Cook took over as Apple chief in 2011 after Jobs stepped down due to a battle with cancer, which claimed his life.

The civil suit filed in 2011 followed the settling of restraint of trade litigation by the US Justice Department due to a "no-poaching" agreement involving an array of Silicon Valley companies.