FILE PHOTO: Elon Musk attends the opening ceremony of the new Tesla Gigafactory for electric cars in Gruenheide, Germany, March 22, 2022. Patrick Pleul/Pool via REUTERS//File Photo

(Reuters) -Proxy firm Glass Lewis has recommended that Tesla shareholders vote against the proposed $1 trillion pay package for CEO Elon Musk, days after ISS also urged investors to reject what might be the largest-ever compensation plan awarded to a company chief.

The Glass Lewis recommendation adds pressure to Tesla's board ahead of a closely watched shareholder meeting on November 6 and renews scrutiny of Musk's compensation after a Delaware court earlier voided his $56 billion pay package.

Glass Lewis said the potential decrease in shareholder value and details of the proposed payment terms "warrant significant concern."

The recommendations by Glass Lewis and ISS "attempt to override the mandate our shareholders delivered to Elon and ignore the staggering financial results delivered under Elon's leadership, elevating their rigid policies over shareholder value," Tesla said in a post on X.

"Glass Lewis's one-size-fits-all checklists undermine shareholders' interests, including by opposing proposals designed to build long-term value at Tesla," the EV maker said.

The two proxy advisory firms had last year also urged shareholders to reject the $56 billion pay package, calling the compensation excessive.

Last month, Tesla's board proposed the compensation plan for Musk in what it described as the largest corporate pay package in history, setting ambitious performance targets and aiming to address his push for greater control over the company.

However, the record pay plan could still hand him tens of billions of dollars even if he falls short of most of its ambitious targets, thanks to a structure that rewards partial achievement and soaring share prices.

Glass Lewis has also opposed a vote on Tesla making an investment in Musk's artificial intelligence company, xAI. While the proxy adviser does not necessarily disagree with the investment, it says that such a "decision needs to be fully considered and ultimately decided by the board, not shareholders."

The proxy adviser's guidance on the pay and investment is part of a wider set of voting recommendations issued on Monday.

(Reporting by Juby Babu in Mexico City; Editing by Maju Samuel)