The U.S. national debt is growing fast and will require massive tax hikes if Congress doesn't act to cut federal spending, Republican lawmakers warned on Thursday.

The national debt has grown from $8.6 trillion four years ago to more than $14 trillion today, said Rep. Jim Jordan, R-OH.

Jordan chairs the Republican Study Committee, which presented a proposal Thursday to cut spending. Joining Jordan at the announcement were Rep. Scott Garrett, R-NJ, the head of the RSC Budget and Spending Task Force, and Sen. Jim DeMint, R-SC, Chairman of the Senate Steering Committee.

The lawmakers said the plan would save taxpayers $2.5 trillion over the next decade. The civilian federal workforce would shrink, and more than 100 budget items and spending reforms would take place if the plan is enacted, the committee said.

A Democratic proposal for a $1.1 trillion omnibus bill failed in December without Republican support. The U.S. federal government is operating on legislation which funds the government only through March.

Unless Washington acts soon to cut spending, massive tax hikes, economic stagnation, and national bankruptcy will rob our children of the opportunity to reach for the American Dream, Jordan said.

The plan would start by reducing spending back to 2008 levels and repeal unspent money from an already approved economic stimulus package, they said.

Starting October 1, the spending would be reduced to 2006 levels and would remain there for the next 10 years, according to the GOP plan.

The White House worked with the RSC last year to include some of the group's ideas in President Barack Obama's proposal for the health reform law which passed last year. House Republicans voted to repeal that law this week.