The National Urban League opposes President Carter's $25 billion tax cut proposal in part because it would pay industries to cut their black employment, league President Vernon Jordan said yesterday.

Carter's plan for an expanded investment tax credit is the villain, Jordan told a National Press Club luncheon.

Carter's proposals call for extending the present 10 percent tax credit on money spent for equipment to cover construction costs as well. He has also proposed letting companies use the credit to offset 90 percent of their taxes in a given year. The current limit is 50 percent.

"What that means," Jordan said , "is that the government, through the tax laws, would offer incentives to industries in that it would pay part of a company's cost to move to accelerate their abandonment of older cities," from an old central-city site to the suburbs. "In effect it is a subsidy to increase black unemployment," he said.

High black unemployment, which averaged 12.5 percent overall and was 41.1 percent for black teen-agers during January, has been a major source of the dissatisfaction that many black leaders, including Jordan, have expressed over Carter's economic policies. White unemployment for January was 6.4 percent.

The Urban League announced its basic opposition to the tax cut plan in mid-January, saying then that too little of the benefits would go to blacks and U.S. cities.

"It is ironic that this proposal comes at a time when the administration is about to announce its national urban policy," Jordan said yesterday.

"Whatever positive measures that policy will include are likely to be offset by tax policies that drain more jobs from the cities. Here is another instance where the right hand giveth and the left hand taketh away."

"In the light of this," he said, "how can anyone claim that civil rithts leaders ougth to be tending to the business of fighting for abstract civil rights when our constituents face economic policies that leave them destitute, without jobs, without human dignity we preach to other nations?"

Jordan told his audience, "There are those who beleive, in John F. Kennedy's phrase, that a rising tide lifts all boats. But we must remind them that a rising tide only lifts those boats in the water, and black people are in the drydock of this economy."