President Carter indicated yesterday he still opposes any rollback of last year's Social Security tax-increase bill, despite warnings by House leaders that Congress may rescind the measure.

In a meeting with out-of-town newspaper editors, Carter said the administration is "trying to hold our tax package together "and prevent any" opening of the entire issue of Social Security again."

At the same time, a spokesman confirmed that the White House was studying the rollback proposal, but said it was only "so that we will be in a position to respond" to Congress.

He said he did "not expect our position appears to heighten the prospect that the administration will run into a full-fledged confrontation with the lawmakers over the payroll tax issue.

Momentum has been gaining in Congress for weeks for a rollback of the December legislation, which has sent voters complaining about higher taxes this year and next. House Democrats are scheduled to debate the issue next Wednesday.

Ironically, Carter proposed last year that the lawmakers move to avert any increase in payroll taxes by shifting the Medicare and disability programs from Social Security taxes to general income taxes. But Congress refused.

Now, with the lawmakers ready to reverse their previous decision, the president is standing firm against going back to his earlier proposal. Most observers expect the White House to cave in if Congress rolls back the increase.

Top presidential advisers reportedly are split over the issue. Treasury Secretary W. Michael Blumenthal opposes rolling back this year's increase. But other Cabinet members seem to be wavering.

Adminstration policymakers fear that if COngress decides to roll back last year's legislation, it may act too hastily in pushing through a substitute and only exacerbate the system's financial problems.

White House officials also are worried that consideration of the payroll tax issue this year may upset the president's tax "reform" package, which still is in the House Ways and Means Committee.