Steve Jobs threatened Palm with patent litigation if it didn't agree to stop hiring Apple employees, a court filing alleges.
The threat was revealed as part of a civil lawsuit brought by five workers against Apple, Google, Intel and others alleging that they were operating an illegal 'no-poaching' conspiracy to drive down wages.
In a 2007 letter to Palm chief executive Edward Colligan, Jobs proposed a no-poaching deal - and implied that if Palm refused, it would face patent litigation from Apple.
When Corrigan responded that he wasn't intimidated, Jobs responded: "My advice is to look at our patent portfolio before you make a final decision here."
The newly-released documents also include a sworn statement from Corrigan, describing a call he received from Jobs that same year.
"In the months before the call, several employees had moved between the two companies. On the call, Mr Jobs expressed concern about employees being hired away from Apple by Palm. As a solution, Mr Jobs proposed an arrangement between Palm and Apple by which neither company would hire the other's employees, including high tech employees," he says.
"Mr Jobs also suggested that if Palm did not agree to such an arrangement, Palm could face lawsuits alleging infringements of Apple's many patents."
And Palm wasn't the only company to receive such communications, with Jobs also writing to Eric Schmidt at Google to ask him to stop attempting to recruit iPod group staff.
Judge Lucy Koh is now considering whether the lawsuit can be granted class-action status - if so, damages could run into hundreds of millions of dollars.
In September 2010, the Department of Justice reached an agreement with Adobe, Apple, Google, Intel, Intuit and Pixar, barring them from entering into no-solicitation agreements for employees.