The Congressional Budget Office said yesterday that key business provisions of President Reagan's tax plan would raise substantially less revenue than the administration had estimated, raising the likelihood that if enacted, the plan would significantly increase the federal deficit.

The CBO reported only on the business provisions of President Reagan's tax plan. It concluded that the four principal business elements of the package would raise $23 billion less between 1986 and 1990 than estimated by the Treasury Department. This would be about a $35 billion revenue loss compared with current law.

Those provisions would raise about the same amount as current law in 1990 and 1991. But during the remainder of the 1990s, they would produce a revenue loss of $14 billion to $19 billion per year compared with the present system, the CBO said.

In another development, White House spokesman Larry Speakes said the administration will propose a "technical solution" to make the tax plan less painful for two-income families with children.

Those families would be hit by the loss of the "marriage penalty" deduction for two-income couples and the conversion of the child-care credit into a deduction, making it less likely that lower rates would offset all of the other changes. Speakes said the administration probably will work out a solution with tax-writing committees rather than submit another proposal.

The disclosure of possible revenue loss, the latest indication that the plan could increase the federal deficit, prompted House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) to say that he will ask the administration to propose tax measures to make up the difference if the CBO's preliminary estimates prove correct.

"I will not ask the committee to begin drafting a House bill until we have complete confidence in the revenue estimates -- and a working agreement with the administration," Rostenkowski said in a statement. "The administration must appreciate the overwhelming reluctance in Congress to proceed on a tax plan that contributes to the deficit."

Treasury Department spokesman Art Siddon said a preliminary analysis of the CBO report showed that the only real difference was over the revenue effect of depreciation write-offs, not the other three provisions examined. The differences on depreciation, Siddon said, mostly stem from different assumptions about such economic indicators as inflation.

The congressional Joint Committee on Taxation also is recalculating Treasury's revenue estimates. Those figures will be more comprehensive than the estimates done by the CBO.

The CBO did not examine the revenue effects of the entire tax plan, which would reduce individual and corporate rates while curtailing numerous deductions and credits. It recalculated only the most important business changes: altering business depreciation write-offs, repealing the investment tax credit, allowing companies to deduct from income 10 percent of the value of the dividends and reducing corporate tax rates.

The estimates do not necessarily mean the entire plan would lose revenue. But for the overall bill to be revenue-neutral, the provisions not examined by the CBO would have to bring in more money than the Treasury estimates.

The revenue loss in the business provisions occurs principally because the economic assumptions used by the nonpartisan CBO are less optimistic than those of the Reagan administration. If those assumptions are correct, total tax revenues would be lower because companies would have less income to tax. Because the economy would be less robust, investors would take advantage of a different mix of tax advantages, possibly reducing revenues further.