Sen. Tom HarkinThomas (Tom) Richard HarkinTrump should require federal contractors to follow the law Orrin Hatch, ‘a tough old bird,’ got a lot done in the Senate Democrats are all talk when it comes to DC statehood MORE (D-Iowa) tore into President Obama on Thursday for "unraveling Social Security."

The liberal senator was unusually tough in criticizing Obama, who Harkin said would deprive the Social Security fund of roughly $100 billion by extending the two-percentage-point payroll tax cut through the end of 2012. That tax funds the Social Security trust fund.

“I never thought I would have to see the day when a Democratic president of the United States and a Democratic vice president would agree to put Social Security in this kind of jeopardy," exclaimed a visibly agitated Harkin from the Senate floor. "Never did I ever imagine a Democratic president would be the beginning of the unraveling of Social Security.”

Harkin predicted that Americans would become addicted to the payroll tax cut, which has been in place since the begiining of last year. The House and Senate are expected to approve the extension on Friday. 

He also noted that under the deal worked out by House Republicans and Senate Democrats, the tax cut will not be offset with other spending cuts or tax increases and will add to the deficit.

"I warn my colleagues to consider the long terms ramifications of these actions," said Harkin. "This continues to open the door to further extending the [pay roll] tax cut because we don't have to pay for it."

The tax cut would save the average American family up to $40 per month by relieving them of part of the tax that is designed to pay their part towards the Social Security fund. 

Obama is a strong advocate for extending the tax cut, which he says is necessary to prevent the economic recovery from stalling. Some economists have estimated the tax cut adds as much as a point to U.S. GDP growth this year.