WASHINGTON (AP) _ Reagan administration refusal to push for cutbacks in copper imports is generating a sharp backlash among Western lawmakers, including two Republican committee chairmen.

''This is what comes from inactive, do-nothing federal government,'' Rep. Pat Williams, D-Mont., told a news conference Thursday. ''What's left is hardball politics between Congress and the White House.''

Sen. Jake Garn, R-Utah, chairman of the Senate Banking Committee, told the news conference he might shelve International Monetary Fund legislation, and Sen. Pete Domenici, R-N.M., chairman of the Budget Committee, said he was leaning toward switching his stand and backing a measure to force sharp cutbacks in textile imports.

''The president is abusing the trust that we gave him to stand up tall and work for America,'' Sen. Max Baucus, D-Mont., told a news conference. ''As a result, we're going to have to do it ourselves.''

The latest flareup in the trade dispute between the Reagan administration and Congress followed release of new figures Thursday showing the U.S. deficit in world trade reached $15.5 billion in September - a record high.

Low-cost imports have caused mine closings and wide layoffs in the Western- based copper industry.

Congress has been urging President Reagan to bargain with Chile, Peru, Zaire and Zambia to obtain copper production restraints. Such ceilings would check the surge in imports from those nations.

Reagan notified Congress on Wednesday that he would not seek such talks, saying copper-producing nations have been unwilling.

Reagan said a lack of restraints would sharpen the U.S. ability to compete in the world market. He also said aid for displaced workers is available from the federal government.

''I just hope they don't need an increase in the IMF quota,'' Garn said. He said that until the administration acts on copper, such a request most likely would be placed at the bottom of his committee's agenda.

International Monetary Fund quotas are the amounts each member of the group, including the United States, contributes to the fund that provides development money to Third World countries. Western lawmakers said copper production overseas is in some cases subsidized by the IMF.

Domenici has joined the administration in opposiition on free trade anymore.''

''I'm leaning very hard not only in the direction of changing my mind and voting for the textile bill but becoming an ardent supporter of things like the textile bill,'' Domenici said.

Meanwhile, Sen. George Mitchell, D-Maine, a leading proponent of rollbacks in shoe imports, issued a statement blaming the White House for the upturn in the trade deficit.

''The policies of this administration are coming home to roost,'' Mitchell said. ''The new trade numbers are just plain scary.''

Sen. Ernest F. Hollings, D-S.C., said in a statement the fresh figures show the ''government does not have control of this trade problem.''

Sen. Lloyd Bentsen, D-Texas, issued a statement saying reduced monthly trade deficits over the summer had raised hopes that the red ink at year's end ''would come at the low end of the estimate.''

''The huge increase in September, though, puts an end to that pipe dream,'' said Bentsen, top Democrat on the Senate Finance Committee's international trade subcommittee.