"The president should demand that Secretary Geithner resign and immediately replace him with someone who will help Washington focus on balancing our budget and allowing the private sector to create jobs," DeMint said in a report Saturday in The Hill.
"For months he opposed all efforts to reduce the debt in return for a debt ceiling increase. His opposition to serious spending and debt reforms has been reckless and now the American people will pay the price," said DeMint, a Tea Party favorite.
Standard & Poor's downgraded the United States' credit rating Friday from AAA to AA+.
"The differences between political parties have proven to be extraordinarily difficult to bridge," S&P said in the announcement downgrading the nation's credit rating.
"Enough is enough," DeMint said in calling for Geithner's resignation.
DeMint also criticized the budget and debt ceiling deal reached by Congress and signed by President Barack Obama.
"The deal Congress just passed over conservative objections has already had its obvious effect, the loss of America's credibility around the world," DeMint said.
The Hill said the White House has no plans to call for Geithner's resignation.
"The bipartisan compromise on deficit reduction was an important step in the right direction," the White House said in a statement Saturday. "Yet, the path to getting there took too long and was at times too divisive. We must do better to make clear our nation's will, capacity and commitment to work together to tackle our major fiscal and economic challenges."