Washington, D.C. ? The competing tax plans laid out by Barack Obama and John McCain would add trillions of dollars to the national debt and could add to the tax system’s complexity, a nonpartisan tax research group concluded in a report released Wednesday.

Both campaigns have insisted that their plans to continue many Bush-era tax cuts and offer new reductions would aid the economy without requiring massive new spending. But the Washington-based Tax Policy Center warned that under either candidate, “the debt would likely continue to rise as it has over the past eight years.”

Obama’s plan – a combination of cuts targeted to middle- and low-income Americans and increases for the wealthy — would increase the national debt by an estimated $3.4 trillion over the next decade, the center reported. Under a similar analysis, McCain’s tax proposals – largely a continuation of the Bush tax reductions – would add $5 trillion. The current national deficit stands at $9.5 trillion.