Mitt Romney's tax plan would provide large tax cuts to the very wealthy, while increasing the tax burden on the lower and middle classes, according to a study released Wednesday.

The report -- produced by researchers at the Urban-Brookings Tax Policy Center -- illustrates just how difficult it would be to recoup government revenue lost under Romney's plan.

The presumptive Republican presidential nominee's tax plan calls for 20% cuts to today's Bush-era income tax rates. He would also eliminate the Alternative Minimum Tax.

Those tax cuts would lead to a sharp decline in government revenue. Y