A maverick newspaper publisher's unusual lawsuit against the California Fair Political Practices Commission (FPPC) today focused attention on an unresolved Carter administration appointment that is strangely reminiscent of the Bert Lance inquiry.

At stake is the confirmation of San Francisco Supervisor Robert H. Mendelsohn, named in May by Secretary of Interior Cecil Andrus as one of his five assistant secretaries.

Mendelsohn has been working at a $169-a-day consultant in the department pending confirmation by the Senate. Sen. Henry M. Jackson (D-Wash.), chairman of the Senate Committee on Energy and Natural Resources, has delayed a committee vote on confirmation pending an investigation into Mendelsohn's campaign finances by the FPPC.

"In all likelihood the committee will act on the Mendelsohn matter within a week," Jackson's press secretary, Brian Corcoran, said today. "This nomination has been around a long time and the senator is anxious to resolve it. Probably, there will be some more testimony at another hearing and then a vote."

The FPPC investigation, still incomplete, has shown the following parallels to the Bert Lance inquiry:

Like the comptroller of currency's investigation into the finances of budget director Lance, the FPPC inquiry has found no violations of law by Mendelsohn. But it has found evidence of fiscal irregularities, including incorrect reporting of four loans to Mendelsohn's unsuccessful campaign for state controller in 1974.

The Mendelsohn campaign committee, reporting on May 19, 1977, some 2 1/2 years after the election said these loans has been forgiven when in fact they had not been. Mendelsohn testified May 20 before Jackson's committee that the loans totaling $8,819, had been forgiven.

As in the Lance case, the issue of alleged political indebtedness has become a central question. In Mendelsohn's case, the most damaging field of inquiry involves a $15,000 loan and related $1,500 contribution given to his 1974 campaign. At the time, Mendelsohn was a member of a Regional Planning Commission.

The FPPC has established that the money came from Transcentury Properties Inc., which then was seeking approval, from that commission for a massive housing developing on the California coastline that was strongly opposed by environmental groups. The money was "laundered" through an intricate process, the FPPC found, and given to Mendelsohn by the sister of a California coastal commission member who favored the Transcentury project.

Commission Chairman Daniel H. Lowenstein said in an Aug. 2 interim report to Jackson that the commission had "not discovered evidence to support a conclusion" that Mendelsohn knew the true source of the money.

Even without this evidence, Mendelsohn is not necessarily home free in his confirmation hearing.One of his responsibilities as assistant secretary is overseeing the Interior Department budget. A Senate source said today that "at the very best" Mendelsohn had shown 'budgetary sloppiness in his campaign financing reports.

The final parallel is the interim report itself. As in the comptroller's report on Lance, the FPPC interim report has been used by Mendelsohn to claim exoneration and used by critics to argue that he should not be confirmed.

The loudest of these critics is Bruce B. Brugmann, publisher of the weekly San Francisco Bay Guardian, who Thursday will file a lawsuit in Sacramento aimed at forcing the FPPC to make public the evidence on which it based its interim report.

"That is a lot worse than Lance in that everything Mendelsohn is accused of doing involves his performance as a public official," Brugmann said today in releasing copies of his lawsuit. "Mendelsohn's in debt to the kind of special interests he'd be overseeing in Washington. He shouldn't be up for this post in an administration that claims to the cleanest since King Arthur's."

Mendelsohn, who flew back to Washington today after attending a tax hearing of San Francisco supervisors here Tuesday night, did not respond to a series of telephone calls seeking his comments.

The San Francisco supervisor has been a target of the Bay Guardian and of some environmental groups for his frequent support of developers while serving as the city's representative on the regional commission charged with regulating coastal development.

After a four-year battle Transcentury finally won approval to build 725 homes at Bodega Harbour, an action which critics say will overwhelm the picturesque fishing village of Bodega Bay and make a mockery of coastal control. Currently, the community has less than 200 homes.

A commission spokesman claimed yesterday that Brugmann's law suit was "frivolous" because the publisher knew that information couldn't be released while the investigation was still continuing.

The spokesman, John Keplinger, said the suit also undermined Brugmann's purpose because it diverted the commission's limited legal resources from the continuing investigation of Mendelsohn.

Commission officials have expressed some irritation with both Mendelsohn and Brugmann for what they regard as selective interpretation of the interim report. The report concluded with this observation: "By this letter the commission does not intend to clear or accuse Mendelsohn or to support or oppose his confirmation."

Corcoran said today that he had no idea of how the Senate committee would vote. But one Senate committee source said Mendelsohn's appointment is in doubt.

"He already was in some trouble and all the questions about the Lance situation haven't made it any easier," the source said.