A veteran Republican policy adviser has been fired from his job at the Environmental Protection Agency after, he said, he tried to end the decision-making isolation of Administrator Anne M. Gorsuch.

Richard A. Tropp, chief counsel to the associate administrator for policy and chief of staff of EPA's policy office, said he was told of his immediate dismissal Friday afternoon. "Half an hour later a janitor was here to change the locks," he said.

Tropp, who worked as special counsel for the Clemency Review Board that President Ford set up to review the cases of draft resisters and held a Ford campaign staff job, blamed his dismissal not on Gorsuch but on "a cabal of half a dozen people" around her who "have deliberately walled her off both from the political appointees within EPA and from the agency's outside constituencies, including its industrial constituency.

"I was trying to get the White House to 'Dutch-uncle' her so that she could break free of that tourniquet around her and become aware of all that's being kept from her," Tropp said. He said his contacts at the White House had met recently with Gorsuch to urge her to be more accessible and forthcoming with her employes and with public. Tropp also worked on the Reagan transition team and was appointed to the policy post last June.

EPA spokesman Byron Nelson said the reasons for dismissals are never discussed "out of courtesy," but added that Gorsuch is not isolated. "She works with people from the White House all the time," he said.

Tropp said those isolating Gorsuch include her staff chief, John Daniel, and her nominee for policy chief, James Sanderson.

The complaint that Gorsuch is hard to reach began almost as soon as she took office last May. Although environmental groups complained most loudly that they were cut off, some business groups and state officials also said they felt the same way. Asked about it at a luncheon with Washington Post staff members last week, Gorsuch replied that to her knowledge, she had met with every responsible group that has asked to see her, "within the constraints of my calendar."