A House appropriations subcommittee issued a conditional death warrant to the Renegotiation Board, raising a strong possibility that the agency, the government's excess profits police force, might be abolished early next year.

The subcommittee unanimously accepted the recommendation of its chairman, Rep. John M. Slack (D-W.Va.), that Congress fund the Renegotiation Board for only half of fiscal 1979 - through next March 31. Slack said later he expected the full Appropriations Committee and the House to go along with his plan.

The subcommittee vote reflected congressional frustration over the board's curious status: although the agency lost its legal authority to perform its sole functions in 1976, it has continued to operate, and to request annual budget increases, ever since.

The Renegotiation Board was created in 1951 on a "temporary" basis to review defense contracts and to recover from contractors excessive profits on government sales. The board was extended regularly until 1976, when Congress let the authorizing statute lapse.

The board has had no power to review new contracts since the statute expired, but it has stayed alive by working at a backlog of cases that built up before then. Last month it asked Slack's subcommittee for a 15 percent budget increase, to $7.3 million, to fund work on the backlog in the coming fiscal year.

Meanwhile, the board's congressional supporters have been trying to find enough votes to win passage of a bill that would extend the authorizing statute and permit the board to go back into full-scale operation. Opponents of the agency have been trying to round up the votes to terminate the board, backlog and all.

The Appropriations subcommittee's action yesterday was designed to break the impasse over the board's future.

"If we didn't decide to stop it, this thing could just flow on like Tennyson's brook," Slack said. "You'd have this government agency, with no authorization, just going on forever because of that backlog.

"We decided to cut them off next March, and that will force a decision one way or the other on the authorizing legislation."

A Senate Appropriations subcommittee will hold hearings today on the board's budget request for fiscal 1979. A staff aide to the subcommittee said the Senate unit might decide to follow the course set by the House subcommittee yesterday.

The House subcommittee's vote yesterday was hailed by opponents of the board.

"There's no group quite as stubborn as a bunch of federal bureaucrats fighting to keep their jobs," said Rep. Mark W. Hannaford (D-Calif.). "But this should spell the end for the Renegotiation Board."

At the board, Chairman Goodwin Chase found something positive in the subcommittee action.

"It would be devastating if they funded us for only half the fiscal year," Chase said. "But I agree this is an effective way to bring action on the bill extending our authority."