Senate Finance Committee Chairman Robert J. Dole (R-Kan.) said yesterday that standby tax increases, a key element in the administration's effort to reduce future federal deficits, are dead in the water.

Dole said "there's no support" on his committee for President Reagan's proposals to levy a 5 percent income tax surcharge and an excise tax of about $5 a barrel on oil beginning in 1986 if the likely deficit then is still higher than acceptable levels.

Dole said he is working on alternative tax increases that would not be contingent on a triggering device.

But he did not elaborate, and said he continues to support the 10 percent income tax cut scheduled for July 1 and indexing of the income tax to offset inflation starting in 1985.

Both provisions are considered essential by Reagan, and the president said in an interview with Business Week magazine made public yesterday that he would veto any bill repealing them.

Dole, however, indicated a willingness to accept postponement or modification of either if necessary to win approval of a larger tax package.

Dole's assessment of the prospects for the administration's triggered tax proposal was strongly supported by other members of the Finance Committee of both parties.

In addition, GOP support for the 10 percent July tax cut and for indexation seemed thin at best, as two senators, John C. Danforth (Mo.) and John H. Chafee (R.I.), questioned whether the two tax reductions enacted in 1981 should be retained.

Democrats are almost certain to press for a limit on the 10 percent cut, so no taxpayer could gain more than $700 a year. In effect, this would scale down the cut for households getting over $50,000 a year in the case of a joint return.

It is estimated that a $700 ceiling would save just under $1 billion this year, $6 billion in 1984 and $8.5 billion by 1988.

Repeal or indefinite postponement of indexing for inflation would save the government $6.2 billion in 1985, $17 billion in 1986 and $30 billion in 1987, according to figures presented yesterday by Treasury Secretary Donald T. Regan.

Dole said he has not worked out any tax increases, but there are several proposals likely to draw his interest.

These include elimination of the deduction for state and local taxes, which would raise about $6 billion a year, restriction of the deduction for nonbusiness, nonmortgage interest, which could raise more than $3 billion a year, depending on the strength of the limitation, and a stretching out of the depreciation schedule for buildings, which could raise as much as $4 billion a year by 1986.

Dole described his intent as seeking to "broaden the base" of the income tax, meaning elimination of some of the special deductions, exemptions and credits on the books, and increased tax compliance, which generally means more stringent reporting requirements and increased powers for the Internal Revenue Service.

Reagan's proposed tax increases would go into effect under a three-step triggering mechanism.

The main step is that the fiscal 1986 deficit as estimated in mid-1985 would have to exceed 2.5 percent of likely gross national product, or about $100 billion.

The deficit for that year is currently projected at $147.7 billion. Without the triggered tax increases, the deficit projection for 1986 rises to about $194 billion.