Amazon.com engaged in a series of skirmishes this year with cash-strapped states that tried to force the ecommerce giant to collect sales tax on online purchases. When the dust settled, Amazon managed to avoid major changes, but with many states continuing to face grim budget scenarios, the battle may not be over.

Now, a Washington, D.C. think tank is slamming Amazon over its stance, saying the company's opposition to collecting sales tax in many states is "simply a desire to maximize the significant competitive advantage it gains over its rivals" and "hurts state and local governments’ ability to finance education, health care, and other services."

The report by the Center on Budget and Policy Priorities, a left-leaning group that focuses on issues affecting low- and moderate-income people, says state and local governments lose more than $7 billion a year because of a 1992 Supreme Court decision that lets online and catalog retailers avoid collecting taxes unless they have a physical presence in the customer's state.

Amazon spokesman Craig Berman didn't immediately respond to a request for comment.

Earlier this year, Amazon led a well-publicized battle with various states that sought to classify Amazon and other ecommerce sites as "physical" retailers (and force them to collect sales tax) based on their ties to locally-based marketing affiliates. These affiliates link to Amazon from their websites in exchange for a percentage of resulting sales.

Amazon played hardball, threatening to dump affiliate programs in states that passed such legislation (thus eliminating the rationale for collecting sales tax). In the end, the company cut off affiliates in North Carolina, Rhode Island, and Hawaii (though it later reinstated its Hawaii affiliates after the governor vetoed a bill there).

The Center on Budget and Policy Priorities says Amazon already collects state taxes on behalf of third party merchants who sell on its website and "calculates and collects sales taxes in every state except one" on internet sales for the Target retail chain — undermining the company's argument that it would be burdensome to collect sales tax across all the states.

And the report suggests that Amazon flaunts the "physical presence" test, saying it collects sales tax in just four of the 17 states where the company or its subsidiaries have facilities.

New York state was the first to establish Amazon as a physical retailer through its local affiliates, and inspired the copycat efforts in other states. Amazon and Overstock.com are challenging the New York legislation in court, though Amazon is in the meantime collecting sales tax in New York.

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