Common Cause charged yesterday that Rep. John M. Murphy (D-N.Y.) solicited $9,950 from maritime interests while his House Merchant Marine and Fisheries Committee was holding hearings on a cargo preference bill that the maritime industry wants passed.

Fred Wertheimer, vice president of the 250,000-member lobbying organization, said Murphy got the money from maritime industry officials and maritime union groups at a June 21 fund-raiser cocktail party the committee chairman held at the Mayflower Hotel here.

On Aug. 2 the Merchant Maritime Committee voted 31 to 5 in favor of the bill, which would require that 9.5 per cent of oil imports be carried on American tankers. Now only about 4 per cent of such imports come on U.S. flagships.

Common Cause, which has lobbied for public financing of congressional campaigns, said it found that 24 of the from maritime unions during their 31 representatives favoring the bill had received $82,263 in contributions from martime unions during their 1976 campaigns.

It said a study of reports filed with the Federal Election Commission showed that the unions gave more than $55,000 to the 1974 campaigns of present committee members, that the unions gave almost $1 million to congressional candidates generally in 1976 and that the industry spent more than $1 million that year on House candidates.

"The maritime industry and the cargo preference bill represent a textbook example for those who wonder how special-interest campaign financing is used to influence government decisions," Wertheimer said.

"The timing of Murphy's Washington fund-raiser was interesting," he added. "This isn't an election year. The fund-raiser came right in the middle of House committee hearings on legislation that the maritime industry considers very important."

Murphy, in a reply to the Associated Press, accused Common Cause of "being used by the major oil companies and foreign-flag shipping interests," which oppose the bill.

He said the maritime interest contributions "had nothing to do with" his support of the bill and that the fund-raiser had been planned "a long time ago." FEC records show Murphy raised $29,650, including the $9,950 from maritime interests, at the party.

Carl Perian, chief of staff of the Merchant Marine Committee, said Common Cause "failed to point out" that Murphy had received from oil industry representatives contributions equal to or greater than the amount he has from maritime interests.

Perian also noted that one contributor at Murphy's June 21 cocktail party was Charles D. Mathews of the Naional Ocean Industries Association, which opposes the cargo preference bill. Mathews was listed in the FEC report that Common Cause distributed yesterday as giving $250.

Wertheimer said he wasn't aware of the Mathews contribution. He expressed skepticism at Perian's statement about oil industry contributions to Murphy. "I'd be interested in seeing the extent of money from the opposition (to the cargo bill)," he said. "There has been a long-standing relationship between committee members and maritime interests."

Perian said that in planning for the June 21 fund-raiser, "we expected that action on the bill would be completed by then." The House is expected to vote on the measure next month. In the Senate it is being considered by the Commerce Committee.

The Common Cause study said Rep. Leo C. Zeferetti (D-N.Y.) got more than any other Merchant Marine Committee member from maritime interests last year - $18,138 from unions and $3,100 form the shipping industry. Neither Zeferetti nor his aides responded to rerquests for comment.

Common Cause also said Rep. Thomas L. Ashley (D-Ohio) received $20,150 - $18,000 from unions and $2,150 from the industry - in 1976. William J. Skow, Ashley's legislative assistant, said the Congressman "has some real reservations about the bill." He voted against it in 1974, when it passed Congress but was vetoed by President Ford.

Skow noted that Ashley declined a request to support the bill this year, declined Murphy's request for his proxy the day of the vote, and did not vote on the measure because, as chairman of the House ad hoc energy committee, he was busy pushing President Carter's energy legislation through the House.