Walmart (WMT) is coming under fire for shortchanging its own employees.

The Cleveland Plain Dealer reported that an Ohio Walmart held a holiday food drive for its own employees—news which actor/producer Ashton Kutcher publicized on Twitter, setting off a Twitter debate with the world’s largest employer.

OUR Walmart—the Organization United for Respect at Walmart—has announced plans for protests on Black Friday demanding better pay and working conditions for Walmart employees and an end to retaliation against activist workers. (The National Labor Relations Board this week accused Walmart of illegally firing workers for protesting against company policies)

Walmart is the largest private employer in the U.S. with 1.3 million workers. Average full-time pay for a Walmart worker: $12.83 an hour. (Walmart does not disclose the number or percentage of full-time vs. part-time workers)

Related: How Walmart Can Make Money Selling 32″ Flat Screen TVs For Under $100

Walmart could pay its employees more if it spent far less on stock buybacks, according to a new report from Demos, a nonprofit public policy organization working for greater political and economic opportunities.

Amy Traub, one of the authors of the report called A Higher Wage Is Possible: How Walmart Can Invest in Its Workforce Without Costing Customers a Dime, told The Daily Ticker that Walmart spent $7.6 billion on share buybacks in 2012 alone.

“If they were to redirect [that] and invest in their own workforce…they could give their low-wage employees a raise of almost $6 an hour each…that would be huge," she says.

She says the Wal-Mart model “isn’t working so well for Wal-Mart these days,” as evidenced by several quarters of declining same stores sales. “Workers across the economy don’t have enough money to shop even at Wal-Mart,” she says.

And despite the share buybacks its stock is underperforming: up 14% year-to-date compared to almost 22% for the S&P 500, 38% for the retail SPDR and 21% for Costco, whose average full-time wage is over $20 an hour.

Walmart has announced that it expects to promote more than 160,000 associates to jobs with higher pay including 25,000 during this quarter but given the size of its workforce Traub says that’s not surprising and it’s "not providing real opportunities for employees."

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