More than 200 cafeteria workers at the House of Representatives, who have unsuccessfully sought the right to unionize, could lose their jobs under a House plan to contract out food services to a private company, officials said yesterday.

Rep. William L. Clay (D-Mo.), chairman of the House subcommittee on labor-management relations, called the timing of the plan "union-busting" aimed at thwarting the years-long union drive by some of the lowest paid employes in government.

Clay said the plan is the latest example of "threats and intimidation" of union supporters, tactics he said would be illegal if Congress had not exempted itself from the National Labor Relations Act.

But a spokesman for George White, the architect of the Capitol, who supervises food service, said that the plan to solicit bids from private firms next month is unrelated to the unionization effort and is part of an economy move being considered at the request of the House Administration Committee, which oversees House operations.

Clay and Rep. Don Edwards (D-Calif.) asked House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) to block the plan and conduct an election to determine if the employes want collective bargaining. Because of its exemption from labor law, Congress does not recognize the right of its employes to bargain.

"The speaker supports the right of these employes to bargain collectively," O'Neill's spokesman Christopher Matthews said. "He is aware of the situation and watching the developments." The Democratic majority on the Administration Committee is to meet today to discuss the food service plan.

Committee chairman Rep. Frank Annunzio (D-Ill.) asked White several months ago to consider soliciting bids for operating the 10 dining rooms, cafeterias and carryouts, said William Raines, White's assistant. White is considering two plans, Raines said, one that would guarantee jobs to current employes and one that would not. He said the committee will decide whether to accept either plan.

Annunzio "simply asked the architect to explore all options," said David Sharman, the committee's staff director. Annunzio "has taken no position" on the issue, he said.

White "has sent out notices telling employes they were free to affiliate with unions but the problem is that we can't recognize unions for bargaining purposes." Clay, who said he may conduct a public investigation, said the law does not prohibit White from bargaining.

Cafeteria workers, whose pay starts at $4.64 per hour and ranges to $10.76 per hour, have long complained about poor working conditions, lack of grievance procedures and threats of disciplinary action and firings -- including threats related to their unionization effort.

About 150 of the 200 have signed union authorization cards, according to Stuart S. Smith, a government public relations officer who helped start the Capitol Employees Organizing Group in 1979. Smith said the group conducted an election in May, and more than 90 percent voted to affiliate with the International Association of Machinists, an AFL-CIO member union that represents thousands of civilian government workers.