The Montgomery County official assigned to investigate questionable practices in the county's Department of Liquor Control has had close contact with at least two key figures in his probe, according to documents he filed with the council.

The official, Andrew Mansinne, director of the council's Office of Legislative Oversight, went on at least two trips with one of the men he is supposed to investigate, Charles Buscher, the former executive at Schenley Industries, Inc., who served as an adviser to Montgomery County Executive Charles Gilchrist on liquor matters. In addition, Mansinne helped Buscher write reports on the Department of Liquor Control and met Buscher at several social events.

One of those events was a luncheon given for Buscher by Mansinne's son, Andrew, at Hogate's Seafood restaurant during the summer. Mansinne's son, a third-year college student, had asked Buscher for information when he was writing a research paper on the issue of whether the government should continue to control sales of liquor in Montgomery County. He turned to Buscher for help on the advice of his father.

"When he told me he was going to write on that issue," said Mansinne, "I offered him advice, the use of my public files, and a suggeston that he interview Mr. Buscher because of his knowledge of liquor control states."

On another occasion, on Dec. 13, 1979, Mansinne attended a birthday party for Gilchrist aide Gerry Evans at the Potomac Inn. The party was given by Charles Buscher. The other guests who attended were Buscher's nephew by marriage, Frank Orifici, who was named deputy director of the Department of Liquor Control several months after the party, Robert Passmore director of the Department of Liquor Control, Gilchrist's wife and Gilchrist's secretary.

Mansinne made his disclosure to the council only a few days after it had awarded him $127,000 to examine questionable practices by the Department of Liquor Control. The previous consultant, Leonard I. Colodny, was fired by Gilchrist after he reported that the department had given an inordinately large amount of business to Schenley, a liquor company that Buscher and Orifici had worked for. Colodny's study cost the county only $5,000.

Council President Scott Fosler has said that he does not think Mansinne's contact with Buscher will jeopardize the investigation, but another council member, Mike Gudis, said yesterday that he wants to ask Mansinne some questions about his meetings with Buscher before deciding whether he should continue with his investigation.

Mansinne has defended his relationship with Buscher say, "I have not been compromised. I will conduct a professional and honest investigation."

But Colodny, the liquor consultant who was fired by Gilchrist, said yesterday that he would not testify before Mansinne in light of Mansinne's contacts with Buscher and Orifici. "His involvement with so many of the people involved in the investigation and the nature of those involvements makes it impossible for me to appear before him," Colodny said. "He should withdraw from the investigation and make himself available as a witness."

Mansinne, in addition to examing questionable purchasing practices by the Department of Liquor Control, is also supposed to look into allegations that Orifici got his merit job in the liquor agency because he is Buscher's nephew. Buscher allegedly used his influence with Passmore, Evens and Gilchrist.

Along with the social functions Mansinne attended with Buscher, he also traveled with Buscher to Annapolis last year, where they met with State Comptroller Louis Goldstein to discuss the tax system, for the county liquor agency, according to Mansinne.

And, in 1978, several months after Gilchrist had been in office, Buscher phoned Mansinne and asked him to meet with him and county attorney Paul McGuckian. At the meeting, Buscher told McGuckian that he had pleaded guilty to illegally inducing state officials to buy Schenley liquor in West Virginia.

In March, when a reporter asked Mansinne his opinion of Buscher acting as an advisor to Gilchrist in light of his misdemeanors, Mansinne defended Buscher. "Responsibility in the corporate sense is different from in the personal sense," he said.

Buscher received a personal fine of $4,500 for his role in West Virginia.