Brushing aside some Republican charges that it was perpetrating the "biggest . . . cop-out in memory." Congress moved yesterday toward putting most of the federal government on stopgap financing until after the Nov. 4 elections.

Almost all of the government would be funded through Dec. 15 at spending levels that the House has proposed for fiscal 1981.Meanwhile, Congress as a whole could defer the actual spending votes until a lame-duck session after the elections.

The plan was approved by the House Appropriations Committee and quickly cleared by the Rules Committee for floor action this week. If the Senate promptly follows suit, there will be little to hold reelection-minded lawmakers in town between now and Election Day, even though Congress is supposed to stay at work until Oct. 4.

Congress nearly always has to put some agencies on stopgap financing when the new fiscal year starts Oct. 1 because it doesn't finish all its appropriations work.

But normally it funds the agencies at the previous year's pending levels, rather than at the almost always higher levels of the new year. And normally, since the start of new fiscal year was shifted from July to October six years ago, only a few agencies -- rather than virtually the whole government -- are forced to continue operating without a specific appropriation from Congress.

This time, 10 of the 13 appropriations bills -- including those for defense and most of the major domestic agencies -- would be funded at 1981 levels. This would mean higher spending levels in most cases, although agencies could not start any new programs that were not funded during 1980.

A consipicuous exception to the more generous financing is foreign aid. No one's favorite piece of legislation at election time, it would be funded at its current level.

Pressure to boost spending to proposed 1981 levels came largely from Rep. Norman Dicks (K-Wash.) and other defense advocates on the Appropriations Committee. With the strong pro-defense mood in Congress, they were believed to have the votes to get their way. The House Democratic leadership reportedly insisted on equal treatment for domestic programs, so a nearly across-the-board increase was approved by the Appropriations Committee.

In both the Appropriations and Rules committees, Republicans sought successfully to chance the date for expiration of the stopgap funding from Dec. 15 to Oct. 18.

This would have forced Congress either to finish its appropriations work by Oct. 18, which Rules Committee Chairman Richard Bolling (D-Mo.) called "totally unrealistic," or to return to Washington in the midst of the campaign's final stretch to extend the arrangement until after Election Day.

In defending the delay before the Rules Committee, Appropriations Committee Chairman Jamie L. Whitten (D-Miss.) said the Dec. 15 date was needed to accommodate the Senate, which has passed only two of the 12 appropriations bills that have been approved by the House.

But GOP House whip Robert H. Michel (Ill.) and other Republicans charged in a letter to their colleagues that the Dec. 15 date would only ensure a lame-duck session and enable lawmakers to face reelection without completing most appropriations bills and other business.