Estimates yesterday comparing 1985 tax liabilities under current law with those proposed by Democratic presidential candidate Walter F. Mondale understated both sets of figures slightly because of a computational error. The increase for a family of four with an adjusted gross income of $200,000 is about $7,888, 13.7 percent; $100,000, $1,761 or 8.1 percent; $50,000, $182 or 2.6 percent; and $35,000, $75 or 2 percent. For a single individual, the same change at $200,000 is $7,063 or 10.8 percent; $100,000, $3,079 or 11.5 percent; $50,000, $428 or 4.5 percent; and $35,000, $97 or 1.8 percent.

Walter F. Mondale today presented a plan to pare the federal deficit by two-thirds in 1989 by cutting $92 billion from government spending and by raising taxes, starting next year, on families with incomes over $25,000.

"Mr. President, all my cards are on the table -- face up," Mondale said. "Americans are now calling your hand. Let's see it. Let's debate it."

The tax increases would fall most heavily on those earning $60,000 or more. But for the first time since he began seeking the presidency, Mondale also specifically called on the middle class to underwrite a portion of the deficit reduction.

Under his plan, families of four earning $25,000 to $35,000 a year would pay an estimated $95 a year more in taxes by 1989; families earning $35,000 to $45,000 would pay $200 more; families earning $100,000 would pay $2,600 more. Corporate taxes would also rise.

Mondale is betting that his willingness to lay out his proposals in detail before the election will attract more votes than the specter of higher taxes will scare away.

Mondale's spending cuts would come from defense, agriculture and health care programs and from government management economies. But the biggest savings -- some $51 billion -- would come from reduced interest payments. His plan calls for $30 billion in new spending.

President Reagan dismissed Mondale's proposal as "nothing new." His administration joined congressional Republicans in an attack on the proposal as an "economic disaster" that would increase the taxes of average Americans.

Mondale's plan would reduce the federal budget deficit in 1989 from a projected $263 billion to $86 billion, or from 4.9 percent to 1.6 percent of the Gross National Product. The $263 billion projection comes from the Congressional Budget Office. The Reagan administration's projection for 1989 is $162 billion, a figure Mondale discredits as "blue smoke and mirrors."

Mondale said that the $85 billion raised in fiscal 1989 from personal and business tax increases would go into a trust fund earmarked solely for deficit reduction.

He also said that he would institute "pay as you go" budgeting, which would require that a source of revenue be found before a spending increase could be proposed by his administration.

"My budget is tough . . . , " he said. "It's a hard, realistic plan, not a wish list."

By contrast, he accused Reagan of being "the biggest spender in American history . . . . When it comes to the deficits, he is neither a moderate nor a conservative, he's a radical," Mondale said. "There's no debt in the history of humanity that even compares to what he's been doing to our economy . . . . This is the hydrogen bomb issue for domestic America."

Mondale said Reagan "whistles right along" running a "happy-talk campaign" because he does not want to reveal his plans to "sock it to" moderate-income Americans with a national sales tax after the election.

Mondale's tax plan contained the following.

*Families earning $25,000 or less would get the full benefits of tax indexing, the law scheduled to go into effect next year that would protect taxpayers from being driven into higher brackets as a result of inflation. Families earning more would be protected to the extent that inflation exceeds 4 percent.

*Mondale would cap the third year of Reagan's tax cuts at the $60,000-a-year level for families.

*A 10 percent tax surcharge would be applied to family income over $100,000 a year and individual income over $70,000.

Together, those three changes would raise $46 billion in 1989, Mondale campaign aides said.

*A 15 percent corporate minimum tax would be enacted, a variety of business tax shelters and loopholes would be closed and tax compliance would be improved, raising $39 billion.

On the spending side, Mondale called for $30 billion in new programs -- in education, environment, research, trade competitiveness and restoration of some of the Reagan social spending cuts.

He would offset those increases with some $122 billion in interest savings and spending cuts. Mondale would slash $25 billion from Reagan's defense budget for 1989, with much of the savings coming from the discontinuation of the MX missile and B1 bomber programs. Under his plan, real defense spending, after inflation, would increase 3 percent to 4 percent a year.

Mondale also plans to cut $12 billion from government health-care costs through a cost-containment program, $4 billion from agriculture programs through a better managed commodity price support system, $5 billion through better government management and $8 billion through reductions in such discretionary programs as concessional arms sales.

In addition, there would be a $51 billion saving by 1989 in federal interest payments, produced by lowering the deficit and a reduction in interest rates. And $17 billion in savings is projected from "growth" in the economy that Mondale says his package will produce.

In January, Mondale had set forth a more modest $100 billion deficit-reduction plan, as opposed to today's $177 billion package. The chief difference is that the new plan raises more in taxes, does not take as big a bite out of the defense budget and calls for more savings in interest payments.

Mondale's blueprint of what the economy will look like in 1989 if his package is enacted is a portrait of pain-free prosperity -- a 3.4 percent growth rate, a 4.8 percent inflation rate, a 5.8 percent unemployment rate and a 7.4 percent interest rate on 90-day Treasury bills.

While most Democrats praised Mondale for the package, some worried the deficit issue is too abstract to register fully with voters.

"The Republicans have never been able to make the deficit spending issue stick to us, what makes us think we can make it stick to them?" asked one prominent Philadelphia elected official.

Mondale pollster Peter Hart said today that the number of people in his polls who expressed concern about the deficit rose from 9 percent to 20 percent during the summer. "That's a lot of legs," he said. "It's the only issue that has dramatically climbed . . . . It's the acid rain on this economy."