NEW YORK (Reuters) - Proxy advisory firm Glass Lewis on Tuesday urged News Corp ( NWSA ) investors to back a plan to end the company's dual-class voting structure, lending additional support to an activist hedge fund's push for the change.

The recommendation comes just days after rival U.S. proxy advisory firm Institutional Shareholder Services last week threw its weight behind the shareholder proposal made by activist investor Starboard Value. Australian governance advisory firm Ownership Matters also recommended that investors vote for the Starboard proposal.

"Allowing one vote per share generally operates as a safeguard for common shareholders," Glass Lewis wrote in its report, which was seen by Reuters.