The Senate Budget Committee recommended yesterday that Congress not rescind the Social Security tax increases scheduled to take effect next winter. It was the first vote in Congress this year against such a rollback, which House Democrats have endorsed 3 to 1.

The Budget Committee, in recommending a $498.9 billion federal spending total for the fiscal year that will begin Oct. 1, voted 8 to 6 on the Social Security question after an impassioned plea by Chairman Edmund S. Muskie (D-Maine).

He warned fellow members against tinkering with the Social Security system for "panicky politicl reasons." Congress voted the increases in the payroll tax only last winter. President Carter opposes a reversal of that vote.

Last week, the House Budget Committee voted to trim $7.5 billion off next year's scheduled Social Security tax levels and replace most of the missing revenues from general funds. The House Democratic caucus also voted overwhelmingly to reduce Social Security tax increases.

The Senate Budget Committee also voted yesterday to support an income tax credit for all fulltime undergraduates, starting at $250 a year and rising to $500 by 1981. Carter opposes that, too.

The tentative spending plan adopted by the Senate committee yesterday and sent to the Senate floor for approval calls for revenues of $443.3 billion and a federal deficit of $55.6 billion. Last week, the House Budget Committee approved the 1979 budget with spending of $500.8 billion, revenues of $443.2 billion and a deficit of $57.6 billion.

Although the House and Senate committees have a similar revenue target, the House wants a tax cut $5 billion smaller than the president's proposed $25 billion tax cut, while the Senate wants a net tax reduction about the same size as the president's.

The House also includes a Social Security tax rollback that neither the Senate committee nor the president wants.

Carter proposes that his tax cut take effect Oct. 1, while the income tax cuts proposed by both the House and the Senate Budget committees would not be in place until Jan. 1.

By May 15, the House and the Senate must adopt a tentative budget resolution that serves as a guide to spending and taxing decisions they make over the summer. By Sept. 15, the two houses must agree on a binding budget whose revenue floors and spending ceilings can be breached only be special vote.

Besides the differences on tuition tax credits and Social Security rollbacks, the budget resolutions proposed by the House and Senate committees are farthest apart on how much to spend on national defense and how much to allot to agricultural spending.

The Senate wants to authorize defense spending about $2.4 billion higher than does the House, while the House recommends farm spending $4.4 billion more than the Senate committee does.

Muskie failed in a last-minute attempt to trim $4 billion from the spending ceiling recommended by the committee.He argued that because the country believes that big federal deficits contribute to inflation, the Senate committee must make a stand against the large deficit and reduce expenditures across the board. He was defeated 8 to 7.