The Senate D.C. Appropriations Subcommittee joined the House of Representatives yesterday in recommending a record-high federal payment for the District of Columbia. Committee chairman Sen. Parrick J. Leahy aid that from now on he would not seek to change the D.C. budget unless there are "substantial federal issues" involved.

"The budget submitted by the city contains primarily local answers to local problems, and it is my recommendation that all of these items be approved," said the Vermont senator, one of the most influential members of Congress regarding D.C. affairs. "This will be my policy in the future."

In approving a $1.5 billion District of Columbia operating budget for 1981 and a record $296 million federal payment, Leahy's subcommittee cut just two items, both of which he said "clearly justified . . . required specific funding and performance levels."

From Mayor Marion Barry's $300 million federal payment request, Leahy cut $1.2 million the District of Columbia had requested to pay interest on short-term borrowing from provate banks to handle cash flow problems.

The city already has authority to borrow such funds from the U.S. Treasury interest-free, and Leahy decided there was no need to begin borrowing from banks and to spend money unnecessarily on interest payments, a Leahy aide said.

Leahy also cut $2.8 million from Barry's request for $9.2 million to increase welfare payments. The reason, the Leahy aide said, was because the District's welfare payments. The reason, the Leahy aide said, was because the District's welfare programs continue to have an error rate much higher than the national average. The money was cut as an incentive for the city to further reduce the error rate, the aide said.

Leahy left intact the remainder of the city's budget for the 1981 fiscal year, which begins Oct. 1.

Leahy's new policy represents a clear departure from prior congressional practice, which was to pore over the District of Columbia budget line by line and cut individual items, and sometimes to impose across-the-board reductions. The House employed both these techniques in recent weeks in arriving at a figure of $290.6 million for the federal payment, which still would be a record high.

The recommendation by Leahy's subcommittee still must be approved by the full Senate Appropriations Committee, which could meet later this week, and by the full Senate. House-Senate conferees must then work out diffeences between the actions by the two chambers.

Still, it seemed likely that the District would emerge with a higher federal payment than ever before. The previous high was in the current 1980 fiscal year, when Congress approved a total federal payment of $276.5 million. f

In a prepared statement, Barry said he was "very pleased" with the action by Leahy's subcommittee, and called the record-high federal payment "critical" to maintaining city services -- which still would suffer sharp cutbacks next year, even if the $296 million payment finally is aproved.

"I view this action as a sign of recognition by the subcommittee of the District's actions to resolve long-standing financial problems while continuing to provide services to residents," Barry said.