Even as a federal judge threw congressional budget-balancing plans for 1981 into jeopardy, House and Senate conferees moved yesterday toward a bigger deficit for 1980 -- provoking some sharp Senate protests.

Tentative approval of additional spending for 1980 drew criticism from Sens. Pete V. Domenici (R-N.M.) and J. James exon (D-Neb.), who warned that the congressional budget-restraint process was being threatened by failure to curb spending this fiscal year.

"In summary, we are being used . . . I think it's a cop-out," complained Domenici.

The outburst came as House and Senate conferees began trying to compromise differences in their separate blueprints for spending during the rest of 1980 as well as 1981.

Both houses have approved balanced-budget plans of more than $600 billion for 1981, although the Senate budget slid into the red by $100 million yesterday when U.S. District Court Judge Aubrey E. Robinson Jr. knocked out the oil import fee that the Senate had relied on to achieve a balance.

For 1980, the House approved spending of $571.6 billion, $5.2 billion more than the Senate voted -- for a deficit of $42.8 billion, or $5.3 billion more than the Senate version.

After a day of slow-moving bargaining on the 1980 budget, the conferees were headed toward increasing spending by $5.7 billion over what the Senate had approved, Domenici complained.

For defense, the conferees approved $135.7 billion, more than either house had proposed. The increase was attributed to larger procurement and other costs than the two houses jointly reflected in their defense proposals.

Domenici said the conferees were being "absolute idiots" in sanctioning such cost overruns instead of sticking with previously approved ceilings.

In response, House members said the increases proposed by the House were required by economic conditions beyond congressional control. "We don't have enough money to do that which we are committed to do," said Rep. William M. Brodhead (D-Mich.).

Rep. Leon Panetta (D-Calif.) warned that "a worse threat to the budget process is not to be realistic" and let restraints collapse under the weight of uncontrollable spending pressures.

House members figure that, even using the higher House figures, there will be only $255 million to accommodate $1.6 billion in spending proposals now moving through Congress, not including up to $500 million in refugee assistance.

Meanwhile, Sen. Ernest F. Hollings (D-S.C.), who was elected by the Senate yesterday to succeed Secretary of State Edmund S. Muskie as chairman of the Budget Committee, said he was not unduly alarmed by Robinson's ruling on the oil import fee.

Hollings indicated he thought the decision might be overturned. As for the Senate's dipping into the fee to balance the budget, Hollings said, "We'll get out of that 'dip' the first chance we get."

Hollings said he was confident the budget would be kept in balance, although the committee's ranking minority member, Sen. Henry Bellmon (R-Okla.), said the balance could be jeopardized by the court ruling.