WASHINGTON — As lawmakers consider rolling back many of the $1 trillion a year in tax breaks now doled out to businesses and individuals, some are promising that streamlining the tax code will not only raise revenue, but also spur economic growth.

But a number of prominent economists cautioned that, while cleaning up the code is a worthy goal, it would do little to stimulate the flagging economy.

The kinds of changes being discussed in the heated back-room negotiations between President Obama and the House speaker, John A. Boehner of Ohio — raising $800 billion to $1.6 trillion in additional tax revenue, along with significant down-the-road spending cuts — would most likely depress growth in the short term.

Longer term, economists said, streamlining the code might improve the allocation of capital enough to raise growth modestly. The overall economy might be 1 to 2.5 percent bigger than it otherwise would be after five or 10 years, translating into perhaps more than one million jobs.