The Senate Banking Committee voted yesterday to deny future subsidies under the government's main housing program for the poor to any area that persists in practicing rent control. The District of Columbia and New York City are two of the major jurisdictions that would be affected.

The committee also voted to cut the number of new assisted housing units for the poor to 150,000 for next year, about 100,000 less than former president Carter had proposed and 25,000 less than even Reagan's plan.

In finishing work on a bill to rewrite and extend for a year the nation's basic housing laws, the committee also approved a provision to require people living in subsidized housing to contribute as much as 30 percent of their income toward the rent instead of 25 percent.

The banking panel's votes were among several taken yesterday in committees on social programs the administration wants to cut back. In other important actions:

The Senate Finance Committee approved, 17 to 2, $10.3 billion in cuts in the next fiscal year in programs for the aged, ill and poor. It would take $1 billion more from such programs than President Reagan has proposed, in part by increasing the premiums for the optional nonhospital part of Medicare and making the elderly pay more out of their own pockets.

A House Judiciary subcommittee voted to preserve -- but with new restrictions on its activities -- the Legal Services Corporation, which gives free legal help to the poor and which Reagan wants to abolish.

The committee decisions came as the House took its first votes on the overall Reagan budget goals for next year. The crucial votes will begin tomorrow.

In addition to its effects on Medicare, the broad measure approved by the Finance Committee would reduce the federal government's minimum share of Medicaid costs from 50 to 40 percent, which could mean losses of millions of dollars for the District of Columbia and Maryland.

The Finance Committee bill, following the president in most matters, also would let states install "workfare" programs to make welfare clients work off part of their monthly benefits; cut Social Security student benefits, minimum benefits, and death benefits; toughen rules for payment of disability benefits and make major reductions in unemployment, welfare and trade adjustment benefits. It would let Medicaid outlays next year rise only 9 percent.

Only Daniel P. Moynihan (D-N.Y.) and Bill Bradley (D-N.J.) voted against the package.

In other action, a House housing subcommittee defeated on a 19-to-13 party line vote an administration plan to merge Urban Development Action Grants, much cherished by mayors, into the existing Community Development Block Grant program, a catch-all, as Reagan has proposed. Democrats on the panel voted instead to keep the two programs separate and provide more money for them then Reagan wants.

The Senate Banking vote on rent control came on an amendment by Sens. William L. Armstrong (R-Colo.) and Alphonse M. D'Amato (R-N.Y.). Their amendment as adopted provides that no new housing contracts under the government's Section 8 housing propgram for the poor be authorized for any jurisdiction that imposes rent control on newly built or newly vacant housing. As both senators stressed, the amendment was written so that people who are now living in rent-controlled housing would not be affected.

Armstrong argued that rent control is a major impediment to the construction of new housing and the saving of decaying older housing because it prevents landlords from obtaining adequate returns on their investment. He said a city that insists on keeping rent control is discouraging enlargement of the housing supply and therefore should not be given the special federal help to build subsidized housing.

D'Amato said that at least 30,000 units of housing in New York go out of use each year because landlords find them unprofitable to maintain.

A Department of Housing and Urban Development spokesman, Assistant Secretary-designate Steve May, said the administration position is that "rent control is a matter of local option and . . . the federal government should not intervene."

But the Republican-controlled committee approved the amendment anyway, with one Democrat, William Proxmire of Wisconsin, joining, to make the final margin 8 to 5.

A District of Columbia housing official, James Aldridge, said in a telephone interview that although new housing is exempt from the rent law, an existing rent-controlled unit remains under rent control when it becomes vacant. A spokesman for New York Mayor Edward Koch said remain under rent control and therefore the amendment would affect the city.