Washington — Over the past year, when asked what they'd do to fix the cracking financial structure of social security, members of Congress and administration officials often gratefully passed the buck: ''I really haven't decided,'' they'd say. ''I'm waiting for the report of the National Commission on Social Security Reform.''
But it's now apparent that the NCSSR is unlikely to produce a gift-wrapped package of repair recommendations. Ironically, many panel members are passing the buck right back where it came from, calling for negotiations between President Reagan and the House Democratic leadership on ways to fix the troubled retirement system.
Without a bipartisan agreement reached through such negotiations, ''we risk a congressional deadlock on social security for the duration of the new congress, '' claims Sen. John Heinz (R) of Pennsylvania, an NCSSR member.
The commission has already made much progress, stress panel members and congressional aides. It has defined the size of the problem - a shortfall in social security of $150 billion to $200 billion through 1990, and a deficit of 1 .8 percent of taxable payroll over the next 75 years.
It has tentatively agreed to recommend compulsory social security coverage for new federal workers and employees of nonprofit organizations, who currently don't have to join the system. And the panel will also probably say that social security should be removed from the unified government budget.
But it is still ''highly unlikely'' that the commission will agree to a narrow package of reforms, says chairman Alan Greenspan. The White House, Mr. Greenspan says, is ''obviously quite interested in what we are doing'' and has been involved in the commission's behind-the-scenes dance of negotiations.
Getting the White House and the House Democratic leadership to negotiate more directly over social security is crucial, in the eyes of many commission members.
''Only with a bipartisan high sign can we get anything through Congress,'' says a commission member's aide.
Without a precleared agreement, the aide says, the Democratic-dominated House will likely forge ahead with a bill that depends too much on increased taxes for the Republican Senate to accept.
But the Reagan administration, which produced a package of proposed social security reforms that quickly vaporized a year and a half ago, may be perfectly willing to let the Democrats take the lead.
''Why should the President want to get involved in social security?'' says a Democratic congressional staffer. ''He's already been burned once. It's Congress's job, anyway.''
A summit meeting between Reagan and House Speaker THomas P. O'Neill Jr. over social security just ''won't happen,'' says the staffer, and the job of instigating reform will fall squarely on the House.
More specifically, it will fall squarely on the shoulders of Rep. Dan Rostenkowski (D) of Illinois, chairman of the Ways and Means Committee, where any social security legislation will originate.
No matter what the national commission recommends, Mr. Rostenkowski indicates he will forge ahead with hearings on the matter in February, aiming to produce a bill by April 1.
''We're going to produce a package, because we have to'' to shore up the ailing system, says an aide to Rostenkowski. ''It's that simple.''