"Dassault Systemes ... today confirmed a media report concerning a trade secrets violation by Siemens Product Lifecycle Management Software, a competitor of Dassault Systemes," the French company said.
"After investigation, Siemens admitted having found a list of 3,216 customer names from Germany, Switzerland and Austria" on the internal computer network of its software subsidiary, the statement said.
Dassault Systemes is the world number one producer of the product lifestyle system, a 3D computer programme that presents the life-cycle of a product from manufacture to maintenance.
Questioned by AFP, a Siemens spokesman rejected the charge that the company had violated trade secrets. It confirmed that it had been contacted by the French company in June about the list. He said the list did not necessarily constitute a "trade secret" and insisted that Siemens "respects the trade secrets" of its rival.
Siemens also said it was "astonished" that after discussions, Dassault had gone public with its allegations.
The Dassault statement said Siemens had since returned the list and promised to destroy any copies.
"Dassault Systemes deeply regrets that information obtained illegally could be found on a competitor's intranet and reserves the right to any action it deems appropriate to enforce its rights."