An investment fund is questioning whether Coca-Cola was upfront about investor support for a new compensation plan after billionaire and top shareholder Warren Buffett said this week he had openly opposed it as "excessive."

“I’m against the plan, and they know it,” Buffett said in Thursday’s Wall Street Journal.

The Journal reported that Buffett’s opposition may prompt Coke to alter the plan, which sets the rules for stock-related awards to about 6,400 Coke executives and managers.

Wintergreen Advisers asked in a letter Thursday to Coca-Cola’s board if executives had shared Buffett’s concerns before the plan was put forth to investors late last month.

Wintergreen, which owns about $100 million of Coca-Cola shares, vocally opposed the pay package before its annual shareholder meeting in April. In the letter, Wintergreen seemed to suggest the Atlanta company purposely touted broad investor support for the plan while ignoring Buffett’s opposition.

“We would like to know whether Coca-Cola reached out to institutional investors before the shareholder meeting to drum up support, even after it knew that its largest shareholder opposed the plan,” wrote David Winters, the New York-based group’s portfolio manager. Buffett’s Berkshire Hathaway owns 9 percent of Coke shares.

Buffett abstained from voting on the plan, which received 83 percent approval from shareholders who voted at Coca-Cola’s annual meeting in April. Wintergreen noted the investors who approved hold less than half of all shares outstanding, since “abstain” votes and shares that aren’t voted aren’t counted.

The Journal reported Thursday that Buffett had expressed his displeasure with the plan, which he said is too dependent on stock options, to several Coke leaders including CEO Muhtar Kent. He said his abstention at the shareholder meeting “was just as clear as voting no” but that he did not want to be seen as attacking management.

Weaker-than-average shareholder support also may figure in any second thoughts Coke is having. Such pay packages usually win more than 90 percent of shareholder votes, according to experts.

In a statement Thursday, Coca-Cola said, “No changes are being made to the plan at this time. The plan already offers maximum flexibility, including the ability to extend the life of the equity plan, to ensure that it continues to meet the needs of the business and remains in line with shareowner interests.”

Coke isn’t likely to issue new stock or option awards until next February, giving the company plenty of time to make tweaks, which could include reducing its emphasis on stock options or spreading the awards over more years. Under the pay plan’s rules, a bigger emphasis on regular shares rather than options would give Coca-Cola a smaller award pool to divvy up.

As currently approved, the package allows Coca-Cola to issue roughly 40 million shares and 300 million stock options over the next four to 10 years to management. Options, which give the owner the right to buy future shares at a fixed price, are worth less than a full share, but can produce dramatically higher investment gains.

Based on the shares and options available, the typical eligible employee could expect in coming years to be awarded about 53,000 Coke shares and options initially worth roughly $700,000. But a handful of top executives usually gets a disproportionate share, reducing totals for those down the ladder.

Some critics were disappointed with Buffett’s decision to abstain. The CFA Institute, a financial analysis industry organization, surveyed members on Buffett’s actions. Of 725 who responded, 64 percent disagreed or strongly disagreed Buffett’s move was adequate to convey his disapproval.

Others were encouraged that Buffett was pushing for changes behind the scenes.

If Buffett succeeds in getting Coca-Cola to trim the management pay plan, “it’s hard to quibble with the result,” said Alex Rue, a longtime Coke shareholder and securities lawyer who is retired from the Securities & Exchange Commission’s Atlanta office.

“It’s one thing to support management,” said Rue, “but it’s another thing when you’re that close to the inside and say “Enough is enough, guys.’ “