WASHINGTON — A Congressional Budget Office analysis released Tuesday predicted that the Affordable Care Act would shrink the work force by the equivalent of more than two million full-time positions and recharged the political debate over the health care law, providing Republican opponents fresh lines of attack and putting Democrats on the defensive.

The nonpartisan budget office’s analysis, part of a regular update to its budget projections, was far more complicated than the Republican attack lines it generated. Congressional Republican leaders called the findings “devastating,” “terrible” and proof that the health care law was a job killer.

The report did say that the law would reduce hours worked and full-time employment, but not because of a crippling impact on private-sector job creation. With the expansion of insurance coverage, the budget office predicted, more people will choose not to work, and others will choose to work fewer hours than they might have otherwise to obtain employer-provided insurance. The cumulative reduction of hours is large: the equivalent of 2.5 million fewer full-time positions by 2024, the budget office said.

The report “rightfully says that people shouldn’t have job lock,” said Senator Harry Reid of Nevada, the Democratic leader. “We live in a country where we should be free agents. People can do what they want.”