Politicians in Washington hardly let a few minutes go by without mentioning how broke the government is. So, it's a little surprising that they've created a stash of more than $1 billion that almost no one wants.

Unused dollar coins have been quietly piling up in Federal Reserve vaults in breathtaking numbers, thanks to a government program that has required their production since 2007.

And even though the neglected mountain of money recently grew past the $1 billion mark, the U.S. Mint will keep making more and more of the coins under a congressional mandate.

The pile of idle coins, which so far cost $300 million to manufacture, could double by the time the program ends in 2016, the Federal Reserve told Congress last year.

A joint inquiry by NPR's Planet Money and Investigations teams found that the coins are the wasteful byproducts of a third, failed congressional effort to get Americans to use one-dollar coins in everyday commerce.

If the mandate to make presidential coins wasn't enough to generate a growing heap of unwanted coins, a political deal ensured that even more unwanted coins would be produced.

It was easier for the bill's sponsor, then-Rep. Mike Castle (R-DE), to move the presidential coin bill forward if it didn't displace other dollar coins honoring Sacagawea, the teenage Native American guide to Lewis and Clark.

The deal: The mint would be required to make a quota of Sacagawea coins. Currently, the law says 20 percent of dollar coins made must have Sacagawea on them.

So, there are now about 1.2 billion dollar-coin "assets" chilling in Federal Reserve vaults, unloved and bearing no interest. By the time the presidential coin series finishes, and there are coins honoring all past presidents, there could be 2 billion.

Several congressional leaders contacted by NPR declined to comment for this story.

Both the Mint and the Federal Reserve provided information for this story, but neither agency would agree to an on-the-record interview.

Delaware's Castle, who left Congress after a primary loss and now practices law, acknowledges that the demand for golden dollars didn't materialize as he had hoped.

Castle says he and others knew when they were passing the bill that widespread adoption of dollar coins would be hindered by the continuing production of dollar bills. But he says that mandating a wholesale switch from bills to coins was politically untenable then, as it is now.

"It's not quite like cutting somebody's Social Security," Castle says, "but politically it's not something the members want to deal with, so it's just very hard to get something like that done."

When Congress was considering the law, the Congressional Budget Office warned that there would be low demand for the coins. The Federal Reserve Board cautioned that coin inventories and storage costs would increase.

Castle says the coins should continue to be produced, but in smaller numbers.

"It's ridiculous to have this kind of over-inventory pile up," he says. "I might actually make some phone calls myself as a result of reading these reports and learning more about what this problem appears to be."

To read the complete article or listen to the radio story, see:$1 Billion That Nobody Wants(www.npr.org/2011/06/28/137394348/-1-billion-that-nobody-wants)