HOUSTON, Feb 22 (Reuters) - Italian electric firm Edison SPA and Portugal's Galp Energia on Thursday asked US regulators to allow them to challenge Venture Global LNG's request for a one-year extension to complete its Calcasieu Pass liquefied natural gas(LNG) facility.

The LNG developer last week asked for a one-year extension to complete its Calcasieu Pass gas-export plant, or to receive assurances it did not need an extension.

Edison and Galp join other Venture Global customers, including BP PLC, Shell plc, and Repsol SA , in asking U.S. regulators for a chance to raise concerns about the proposed extension.

Galp also wants documents that Venture Global filed under privilege released to it so it can evaluate the LNG developer's request for the extension.

"It should be beyond dispute that documents related to the status and progress of construction are relevant to a request for extension of time to complete construction," Galp said in its letter to the Federal Energy Regulatory Commission (FERC). (Reporting by Curtis Williams in Houston Editing by Mark Potter)