A House hearing on a proposal to let hospitals use Medicare funds to hire consultants who specialize in union-busting turned bitter yesterday, with one member suggesting proponents of the provision might prefer to go even further and return to slavery.

The flare-up came between sharp-tongued labor-management subcommittee Chairman Phillip Burton (D-Calif.) and Rep. Eugene Johnston (R-N.C.), who is a member of the panel and supports the Reagan administration's decision to let hospitals hire the anti-union consultants, which they sometimes do to help hold down wages. The Carter administration had forbidden use of Medicare funds for such purposes.

Johnston argued that a hospitals' use of Medicare funds to keep unions out and labor costs down was a legitimate use of federal dollars.

Burton facetiously responded that Johnston could take his idea further. "The cheapest of all of these cost reduction formats would be to have a form of slavery. Then, this would really cut the labor costs as a part of providing the medical services," Burton said.

"I have never regarded the chairman as a staunch defender of the taxpayers," Johnston replied. "But I will suggest that that idea will be of great benefit to the American taxpayer. If you want to put it forward, I will be delighted to second it."

The congressman "was just joking," a spokesman, Doug Clark said for Johnston later. "He was just trying to turn it around on Burton, realizing that Burton would never put forward such a proposal." But Johnston also realizes "that, perhaps, subcommittee meetings are no place to joke. He is sorry for any misconceptions," Clark said.

The joke did not go over very well with union representatives, who argued before the panel that the use of Medicare funds to help block union campaigns will cost the government $30 million annually at a time when the administration is reducing federal spending for health care.

"Apparently, feeding the elderly poor and ministering to their health care needs is not a proper or desirable object of federal funding, but preventing workers from improving their wages and working conditions is," said Arnold Mayer, international vice president of the United Food and Commercial Workers union.

Paul R. Willging, deputy administrator of the Health Care Financing Administration of the Department of Health and Human Services, denied that charge.

"We are not supporting one side or the other in the collective bargaining process," Willging said. He said that, under the Reagan administration, Medicare payments to hospitals are "based on the reasonable costs incurred to provide covered services to Medicare beneficiaries."

Those "reasonable costs" include "the costs of retaining consultants and attorneys to familiarize" hospital administrators with federal labor law and such matters as union organizing, Willging said.