WASHINGTON —Sen. David Vitter joined Tuesday those opposing and seeking answers on any potential “carbon tax” that could be proposed by Democrats in Congress or by President Barack Obama.

Vitter, R-La., wrote a letter to Treasury Secretary Timothy Geithner supporting a public records request and lawsuit filed by the conservative Competitive Enterprise Institute, which seeks at least 7,300 emails with the word “carbon” sent to or from the department’s Office of Energy and Environment.

The Obama administration has not publicly proposed a “carbon tax,” which is a fee on corporations that release greenhouse gases, or “cap-and-trade,” which allows companies with emissions below their permitted cap to sell the extra capacity on their permits to companies releasing more pollutants.

Vitter said Obama’s re-election likely makes him “emboldened” enough to push such environmental policies. “I just think it’s important for the American people to know,” Vitter said Tuesday in a phone interview, noting that Obama has previously backed cap-and-trade policies that died in Congress.

Hurricane, or Superstorm, Sandy, and other recent weather phenomena have recently highlighted national global warming and greenhouse emissions debates.

The Treasury Department is seeking to charge the Competitive Enterprise Institute about $1,400 for the reprinting and distribution of the thousands of emails requested. The nonprofit institute filed a lawsuit for the documents.

Vitter said the efforts to charge so much money at least “circumvents” the spirit of federal public records laws.

“It’s really troubling that Treasury is attempting to hide their involvement, and they need to be called out,” Vitter said in his announcement. “I want to know why they’re avoiding transparency obligations, but they also need explain their economic reasoning to the American people who will ultimately be paying much higher energy costs.”

As of Tuesday afternoon, a Treasury Department spokeswoman stated that the department had not yet received Vitter’s letter and the Treasury officials refused further comment on the letter and records request for now.

While such “cap-and-trade” or “carbon tax” proposals are designed to reduce greenhouse gas emissions in the country, critics like Vitter have argued they would dramatically increase gas and utility costs for Americans, including the most financially needy.

In his letter, Vitter also requested the most recent Treasury Department analysis on the impacts of “energy taxes,” specifically of a “carbon tax.” In addition, Vitter asked what regions of the nation would be most affected by such emissions fees and what analysis has been done on how energy producers would “pass on the costs of such a tax.”