Loopholes in the current federal lobby disclosure law have allowed the energy companies to "hide more than they disclose" about their "multimillion-dollar lobbying campaign on President Carter's energy package," Common Cause charged yesterday.

Common Cause, which calls itself a public interest lobby, released a study of lobby disclosure reports by energy-related organizations during the first nine months of 1977, when Carter's energy package was being fought out in Congress.

The law is so full of loopholes that, according to the Common Cause study:

Not one of the seven major oil companies registered as a lobbyist and only one in 10 energy-related organizations registered, since the law requires only groups whose "principal purpose" is lobbying to register.

The law did not require Mobile Oil to report $4 million spent on "advocacy" advertising in relation to energy, and does not require reporting of activities aimed at getting the "grass roots" to lobby congress.

Cumulative spending reported by the gas and oil industry is "misleading low." The oil industry reported spending "only $600,000" and the gas industry $500,000. Common Cause, with a $5 million budget, reported spending $1 million, while the American Petroleum Institute, with a 1977 budget of $30 million, reported spending "only $274,900."

Among the individual energy lobbyists identified by Common Cause, fewer than half file lobby reports with Congress.

Expenditures reported by lobbyists are sometimes so low as to be meaningless. Several full-time lobbyists reported expenditures of less than $10 during the quarterly period, the report said.

Common Cause President David Cohen termed the lobby disclosure requirements "a charade" and called for enactment of a tougher lobby disclosure law.

A House subcommittee has reported a bill that would tighten the provisions in the lobby disclosure law. The House Judiciary Committee is expected to mark up the bill in a couple of weeks. A Senate Governmental Affairs subcommittee is expected to consider a similar bill soon.

A revision of the lobby disclosure law passed both the Senate and the House in 1976, but died in conference.

According to Common Cause, any new law should require reports by organizations, not individuals; should cover all groups that engage in significant lobbying; and should include meaningful reports on expenditures, advertising and mass-mailing efforts.

The study said that under a tighter California law "the same oil companies which don't register as lobbying groups under federal law report spending hundreds of thousands of dollars to influence California decision-making."

"In 1976, for example, Standard Oil of California reported spending $292,933, Union Oil $146,876 and Mobil Oil $107,540 on California lobbying a total of $547,349, only $90,000 less than the entire oil industry reported spending on federal lobbying during the first nine months of 1977."

The gas and electric utilities reported spending $930,968 on California lobbying in 1976, "one and a half times as much as the $507,047 the entire gas industry reported spending during the first nine months of 1977 on their federal lobby disclosure reports," the study said.