The House ethics committee opened a preliminary investigation into allegations that Rep. Austin Murphy (D-Pa.) allowed someone else to cast votes for him while he was absent from the House floor.

The committee, which opened the probe following a report published six weeks ago, also is investigating allegations in the report that Murphy circumvented House financial disclosure rules and hired "ghost" employes who are paid for little or no specific work.

Murphy, first elected in 1977, said in a statement he is "confident that the preliminary inquiry will find that there are no grounds for the allegations that have been made. I am hopeful that the inquiry will also serve to expose those who have made these self-serving charges."

The committee, in a brief statement, said the various allegations, if true, would be violations of the law or the House's code of conduct.

The panel, which never comments publicly on evidence until final action is taken, said only that it had "been presented with information suggesting that Rep. Austin Murphy may have permitted votes to be cast in his name at times when he was not present in the House of Representatives, failed to fully disclose holdings under the Ethics in Government Act, favorably treated, or accepted favors or benefits from, certain individuals and improperly used official staff."

In early May, The Washington Times reported it had discovered Murphy had allowed another member of Congress to cast votes for him while Murphy was not in Washington. The report said Murphy was in Pennsylvania on July 14 and Aug. 9-10, 1978, but was recorded as voting 21 times on those days.

Quoting a former staff member, the newspaper said a top aide on several occasions gave Murphy's voting card, with Murphy's approval, to another member.

The newspaper, citing past and present aides as sources, also reported that Murphy stacked both his personal and subcommittee staffs with friends and ghost employes, that he hired a colleague's sister, that a lawmaker employs Murphy's daughter, that he allowed or condoned the filing of questionable expense vouchers, and that he gave false information in reports to committees about friends he hired for a subcommittee.

The Times also said he leased a domestic station wagon from a ghost employe at a price comparable to what is charged for a luxury car, used two ghost employes to perform personal chores such as cutting his grass and cleaning his swimming pool, and may not have accurately reported his financial holdings.