Proxy advisory firm Institutional Shareholder Services (ISS) urged Apple Inc. investors to vote against Chief Executive Officer Tim Cook's remuneration, citing concerns around the magnitude and structure of his equity award.

Apple will hold its annual shareholder meeting in the first week of March.

"There are significant concerns regarding the design and magnitude of the equity award made to CEO Cook in FY21... Half of the award lacks performance criteria," ISS said in a letter.

Cook took home $3 million in salary in 2021. In addition, he received $82.3 million in stock awards, $12 million for hitting Apple's targets, $1.4 million for air travel, 401(k) plan, insurance premiums and others.

In total, he earned $98.7 million in 2021, compared with $14.8 million a year earlier.

He received 333,987 restricted stock units, in his first stock grant since 2011 as part of a long-term equity plan. He will be eligible to receive additional units in 2023.

ISS valued Cook's 2021 equity award at $75 million. His pay was 1,447 times that of the average employee at the tech giant, according to a filing disclosed in January.

"Half of the $75 million award is purely time-based, and the award would continue to vest in full in the event of his retirement," ISS wrote.

Apple was not immediately available for a comment.