WASHINGTON — Special interest groups with the biggest stake in President Clinton’s proposed national health insurance reform legislation are pouring big bucks into the coffers of politicians, a Washington-based public interest group said Monday.

Citizen Action, a group founded by consumer advocate Ralph Nader, reported that political contributions from health and insurance industries rose 31 percent between 1991 and 1992 — from $4.2 million to $5.6 million. The industries currently are amassing a $15.5 million war chest for future campaigns, Citizen Action said.

Senate Majority Leader George J. Mitchell is the biggest beneficiary of health and insurance contributions, the group’s analysis indicated. So far this year, those special interest donors have contributed $87,950 to Mitchell’s 1994 re-election campaign. Health and insurance special interest groups and individuals have contributed $443,483 to Mitchell since 1979, when the breakdown of industry donations began.

The Public Citizen analysis indicated that Mitchell returned one $3,000 donation from a hospital political action committee. In addition to being majority leader, Mitchell is a member of the Senate Finance Committee, which will play a key role in shepherding the president’s bill through the Senate. Public Citizen noted that Finance Committee members received the largest single bloc of health care contributions.

The second largest recipient of political contributions from hospital and insurance interests was Sen. William S. Cohen, who is not up for re-election in 1994. Cohen received no political donations from those groups in 1993, but has accepted a total of $190,091 since 1979.

Rep. Olympia J. Snowe and Rep. Tom Andrews, both facing re-election next year, reported smaller contributions from health and insurance donors. Snowe took in $4,850 this year, and has accepted $124,354 since 1979 from those industry contributors. Andrews received $2,850 in contributions this year, and has taken in $77,720 from health and insurance donors since winning election to Congress three years ago.

All four Maine delegation members have endorsed different health care reform bills. Mitchell supports the Clinton plan introduced to Congress last month. Cohen backs a GOP alternative sponsored by Sen. John Chaffee, R-R.I. Snowe is a co-signer of a Republican plan written by Rep. James Cooper, R-Tenn., and Andrews backs a House offshoot of the Clinton plan.

Citizen Action said the political contributions will help the insurance and health industries protect their interests during debate over health care reform.

“The health and insurance industries have showered key members of the House and Senate with nearly $6 million in the last 10 months,” said Michael Podhorzer, Citizen Action’s campaign director. “It would be the height of illogic to believe that these special interests are not expecting anything in return.”

Citizen Action’s report covered the first 10 months of 1991’s election cycle. The same period of this past election cycle ended Oct. 31.

The leading Senate recipients of contributions for Jan. 1 through Oct. 31, 1993, were: Kay Bailey Hutchinson, R-Texas, $377,069; Daniel P. Moynihan, D-N.Y., $140,370; Joseph Lieberman, D-Conn., $139,600; Orrin Hatch, R-Utah, $130,700; and John Chafee, R-R.I., $124,125.

Leading House recipients were: Rep. Jim Cooper, D-Tenn., $163,846; Fortney Pete Stark, D-Calif., $100,700; Richard Gephardt, D-Mo., $90,401; and Dan Rostenkowski, D-Ill., $77,000.