Mr Ballmer said, "Just tell me it's not Google," to Lucovsky, whose title at Microsoft was 'distinguished engineer'.

Lucovsky replied that he was joining Google.

"At that point, Mr Ballmer picked up a chair and threw it across the room hitting a table in his office," Lucovsky recounted in a sworn declaration.

The 16-year Microsoft veteran, added that Ballmer then launched into a tirade against Google CEO Eric Schmidt.

"I'm going to f***ing bury that guy, I have done it before, and I will do it again. I'm going to f***ing kill Google," Ballmer reportedly said.