WASHINGTON — Single-use plastic bags, a staple of American life, have got to go, the United Nations' top environmental official said Monday.

Although recycling bags is on the rise in the United States, an estimated 90 billion thin bags a year, most used to handle produce and groceries, go unrecycled. They were the second most common form of litter after cigarette butts at the 2008 International Coastal Cleanup Day sponsored by the Ocean Conservancy, a marine environmental group.

"Single use plastic bags which choke marine life, should be  banned or phased out rapidly everywhere. There is simply zero justification for manufacturing them anymore, anywhere," said Achim Steiner, executive director of the U.N. Environment Programme. His office advises U.N. member states on environmental policies.

Steiner's declaration accompanied a UNEP report that identifies plastic as the most pervasive form of ocean litter. According to the report, "Plastic, the most prevalent component of marine debris, poses hazards because it persists so long in the ocean, degrading into tinier and tinier bits that can be consumed by the smallest marine life at the base of the food web."

The ban is already being tested in China, where retailers giving out thin bags can be fined up to $1,464. According to one nationwide survey, 40 billion fewer plastic bags were given out in grocery stores after the law's enactment. In addition, Ireland managed to cut single-use plastic bag consumption 90 percent by levying a fee on each bag that consumers use.

In the United States, only San Francisco has completely banned plastic bags. Los Angeles will do so in 2010. Also, Washington, D.C.'s city council is set to vote on a five-cent-a-bag tax later this month. On first reading, the bill passed unanimously. Similar proposals have failed in New York and Philadelphia.

Keith Christman, senior director for the plastics division of the American Chemistry Council, responded that the term "single-use" is misleading because most people actually reuse plastic bags, "for example, to line their trash cans."

"A ban on plastic bags could also cause some unintended consequences," he said. In particular, the increased demand for paper bags would double greenhouse emissions and create "a dramatic increase in waste," Christman said.

Leading U.S. plastic bag manufacturers aim to increase the recycled content of plastic bags to 40 percent by 2015, he added. That would reduce plastic waste by 300 million pounds a year.

"Recycling is what we see as the best approach for the U.S.," Christman said. "Plastic is just too valuable to waste.