Four Silicon Valley companies including Apple and Google have failed to persuade a US judge to sign off on a $350 million settlement to resolve a lawsuit by tech workers, who accused the firms of conspiring to avoid poaching each other's employees.

In a ruling on Friday, US District Judge Lucy Koh in California said the class action settlement was too low, given the strength of the case against the companies. Intel and Adobe were also part of the proposed deal.

No leaving Apple: Steve Jobs allegedly stopped employees from being offered jobs elsewhere. Credit:Bloomberg

There is "substantial and compelling evidence" that late Apple co-founder Steve Jobs "was a, if not the, central figure in the alleged conspiracy," Koh wrote. The judge provided details in evidence of anecdotes involving Jobs and other Valley executives to show why she thought the workers deserved more.

Representatives for Apple and Google declined to comment. Intel spokesman Chuck Mulloy said the company was disappointed Koh rejected an agreement "that was negotiated at arm's length over many months," but appreciated that Koh provided additional information on her views.