Donald Trump’s tax-cut plan could add as much as $24.5 trillion to the national debt over the coming 20 years unless it is accompanied by steep cuts in spending and entitlement programs, a new analysis finds.

The paper published by the Tax Policy Center, a joint venture by the Urban Institute and Brookings Institution, provides a sobering reminder that many of the generous tax cut plans being floated by Trump, former Florida Gov. Jeb Bush and other candidates carry enormous long-term price tags. Some of them, if adopted, would spark a renewal of the long-term debt crisis and could undermine the very economic recovery that GOP and Democratic presidential candidates alike are promising.

Related: Experts Predict Rising Deficits and Debt in GOP Candidates’ Tax Plans

The numbers are startling, according to the new report: Trump’s proposals for consolidating and slashing individual and corporate tax rates and getting rid of the estate tax would reduce federal revenues by an estimated $9.5 trillion over the coming decade and an additional $15 trillion over the subsequent 10 years. And that’s before accounting for the government’s added interest costs from having to borrow substantial sums to make up for the revenue shortfall and keep the government operating.

Under Trump’s plan, income taxes would be eliminated entirely for millions of single Americans who earn less than $25,000 a year and married couples making less than $50,000 a year. Trump pledged that individuals would receive a new, simplified one-page form to send to the IRS saying, “I win.”

He would collapse the number of income tax brackets from seven to four, with the highest marginal tax rate reduced from the current 39.6 percent to 25 percent. Businesses ranging from major corporations to tiny operations would also have their rates cut to no more than 15 percent, from the current corporate rate of 35 percent.

Finally, Trump has pledged to eliminate the estate tax – which would be a boon to farmers and ranchers as well as average Americans.

The Tax Policy Center found that about two-thirds of the overall revenue lost under that plan would result from lowering income tax rates and roughly a third from cutting corporate tax rates. Taxpayers at every income level would benefit, but the wealthiest Americans would benefit most — both in an absolute dollar term and as a percentage of their income. Trump has said that most Americans “will love” his tax plan, and that it would greatly improve economic incentives to work, save and invest.

"It'll grow the American economy at a level that it hasn't seen for decades, and all of this does not add to our debt or our deficit," Trump said of his tax plan during a news conference in late September.

The billionaire businessman said he would couple his tax plan with savings from elimination of wasteful government spending, by renegotiating Obama administration trade deals and by insisting that our allies reimburse the government for the cost of U.S. military installations and protection. Trump has also said he would offset part of the cost of the tax cuts by eliminating most deductions for individuals and businesses and by imposing a one-time tax on corporate assets held abroad.

Related: Trump Vows Lower Tax Rates, Revised Trade Agreements, Deep Spending Cuts

But tax and budget analysts and government watchdogs are highly skeptical that Trump and other candidates could come close to offsetting the impact of their tax cut schemes.

“If you wanted to cut spending to offset these tax cuts you’d have to eliminate all of national defense and still a bunch of discretionary spending or spending on Medicare and Social Security to do it,” Tax Policy Center Director Leonard Burman told reporters on a Tuesday call, according to the Washington Post.

Trump said in April that he opposed cutting Social Security and other entitlement programs. Moreover, the Tax Policy Center included Trump’s promised elimination of tax deductions and some loopholes into its calculations, though its calculations involved some assumptions to be able to model out details not fully specified in Trump’s proposal.

The Tax Policy Center study concludes that without substantial offsetting cuts or savings, Trump’s tax cuts would increase the national debt by nearly 80 percent of the Gross Domestic Product by 2036. At the same time, the huge drain on the treasury would undermine some or all of the economic incentives being sought.

Related: 9 Insights on Debt, Taxes and the Economy from a Former CBO Director

Robert Bixby, executive director of the Concord Coalition, an anti-deficit group, complained that Trump’s massive tax cut plan “distorts public expectations by giving people the idea that we’re back in 2000 again and we have a big budget surplus — and we don’t.”

The perception problem is compounded by a very real one, Bixby said: “There’s still no magic way to pay for tax cuts. These kind of proposals really get in the way of a realistic discussion about the budget, because they lose so much revenue that you would have to cut even more spending that would be needed just to get back to a balanced budget or a sustainable budget.”

Related: New CBO Director Renews Warning on Long-Term Debt

This fall, the independent Tax Foundation did a similar analysis of Trump’s tax plan and found that it would cost $11.9 trillion over the coming decade under “static” scoring that doesn’t take into account likely economic growth from changes in tax policy. When likely growth was factored in, Trump’s tax cuts would cost somewhat less — $10.1 trillion, according to the Tax Foundation.