The inspector general at the Environmental Protection Agency, Matthew N. Novick, whose job is to ferret out wrongdoing in the embattled agency, has been criticized by some members of Congress for failing to fully investigate major allegations of favoritism and mismanagement while focusing on more petty charges.

In particular, five House Democrats have charged that Novick mishandled an investigation of Denver attorney James W. Sanderson. He was accused of improperly aiding legal clients while serving as a paid, part-time adviser to EPA Administrator Anne M. Burford, who changed her name from Gorsuch when she was married Sunday. Novick found no evidence of wrongdoing by Sanderson and turned the matter over to the Justice Department, which is still investigating.

Novick himself is being investigated by the General Accounting Office for allegations that include using government employes to do personal work. Such charges and countercharges have become typical of the increasingly poisonous atmosphere inside EPA.

Novick has strongly denied the allegations against him, saying they are being spread by EPA employes upset about transfers and downgradings. The 20-year career investigator said he is required to look into every allegation that comes his way, no matter how trivial.

Novick said he saved the government more than $400 million last year by focusing on contract audits. The Reagan administration was embarrassed last week by Novick's critical audit of EPA's $1.6 billion hazardous waste cleanup fund. It showed that EPA used some of the cleanup money for other purposes and could not account for $53 million of the $180 million spent altogether last year.

Novick said he has just 28 staff investigators and was never informed of conflict-of-interest and mismanagement charges now swirling around EPA's hazardous waste program. EPA sources also said that Burford has deliberately limited Novick's role by separating EPA's enforcement functions from the inspector general's office.

Still, congressional critics claimed Novick's limited probe of Sanderson stands in marked contrast to the way his office aggressively pursued minor allegations against EPA whistle-blower Hugh B. Kaufman. The five House members, including Reps. James H. Scheuer (D-N.Y.) and Patricia Schroeder (D-Colo.), said Novick's conclusions in the Sanderson probe "are refuted by the evidence in the report itself."

Although Sanderson was accused of influencing a water standard that clearly affected one of his clients, the Denver Water Board, Novick found that none of Sanderson's clients had any matters pending at EPA. The congressmen complained that Novick never questioned Burford, never looked into charges about Sanderson's use of EPA vehicles, and never examined most of Sanderson's legal billing records.

Sanderson said yesterday he was never involved in the Colorado water issue. "It's all a bunch of unsubstantiated charges," he said. "The IG's people concluded there was no basis for the charges. Nobody at Justice has talked to me ever, and it really irritates the hell out of me, since I'm the one who's being maligned."

Sanderson said that Schroeder keeps reviving the issue, in part because he ran the campaign of the Republican challenger for her congressional seat in 1980. "The only thing I can figure out is that she has carried a grudge against me," he said.

Novick said he did his job by compiling six volumes on the Sanderson charges and turning them over to Justice. Some of Novick's critics added that he has become more aggressive in recent months.

According to some EPA officials, the root of Novick's problem is Burford's separation of EPA's enforcement functions from the inspector general. This means that EPA employes who run programs on hazardous waste and air and water pollution also decide whether companies should be prosecuted for violating the law.

Some EPA officials, who do not want to be identified, contend that there is an inherent conflict of interest in employes acting as both managers and prosecutors. They said this helped prompt charges that the hazardous waste office arranged "sweetheart" settlements with polluters rather than taking them to court.

The enforcement division is headed by EPA general counsel Robert M. Perry, a senior policy maker who is close to Burford. Perry, not the inspector general, decides whether to pursue many criminal cases. He also advises Novick on pending investigations, including those of top agency officials. Novick's office has not been assigned a lawyer.

"I have made strong objections to this," Novick said. "I have tried to get the general counsel to allow me to hire my own lawyer." In only one instance--a case examining involvement of both Burford and Perry with lead refiners--was Novick allowed to hire a lawyer temporarily.

EPA sources said Burford refused Novick's request last year to give him authority over the agency's enforcement actions. "Perry's role is to protect the administrator," said one investigator. " Burford wants an aggressive inspector general everywhere but in the enforcement area."

The GAO is now examining the independence of Novick's office, as well as the charges against Novick. These include allegations, first reported in the Chicago Sun-Times, that Novick used his EPA driver, Carl Martin Jr., for personal errands.

Novick said he had Martin transferred to his office because he often needs a driver, but that Martin also drives other employes and works as an office clerk. Novick said he has asked Martin to buy him stamps, but only during official trips to the post office. Novick said he paid Martin privately to drive him to the airport for a Florida vacation.

Another allegation is that Novick had a secretary in his office type personal letters and his son's term paper. Novick said he paid her to do this work on her own time.

GAO also is looking into an allegation that Novick helped a woman friend obtain a job as a space planner in the office of former hazardous waste chief Rita M. Lavelle. Novick said he notified Lavelle that he was dating the woman and that he didn't want this to influence her selection. He said the relationship had nothing to do with the fact that he has not begun any investigations of Lavelle's office.

Novick also denied congressional charges that he engaged in a political vendetta against Kaufman, the EPA whistle-blower. Novick said he initially declined Lavelle's demand that he investigate Kaufman, and that Lavelle expressed amazement that an employe could publicly criticize the agency without being fired.

But when Kaufman mistakenly applied for sick leave for a speaking engagement in Pennsylvania, he was tailed and photographed by EPA investigator Richard Walsh and observed checking into a motel with a woman who turned out to be Kaufman's wife. Novick made no apologies for approving the purchase of the camera, saying: "It's rare we have an opportunity to prove in advance that sick leave was abused. We have an agency riddled with people taking sick leave on Monday and Friday."

The controversy didn't end there. Walsh received a poor performance rating for recording in his notes that Novick aide James Conn had told him Lavelle wanted Kaufman fired. Novick later announced that he was transferring Walsh and closing the Philadelphia office for efficiency reasons. Walsh has filed a grievance asking that Novick's "vindictive" action be canceled.

As for Conn, Novick later downgraded him for urging investigators to destroy their files to avoid similar embarrassing disclosures under the Freedom of Information Act. Novick said such advice in no way represented his policy.

In another probe last year, Novick found that former research chief Andrew P. Jovanovich "gave a strong appearance of preferential treatment" by helping a business associate to get a $77,000 grant that already had been rejected by an EPA peer review panel. Jovanovich denied any wrongdoing, and Burford placed him on paid leave for six months and finally transferred him to a science adviser's job.