The House yesterday began debating a bill designed to broaden competition for drilling leases on the outer continental shelf and to permit the government to explore underwater oil and gas fields to determine their worth before leasing them.

The Carter administration and congressional supporters contend the bill would expand the number of oil producers offshore, assure that the United States is fully compensated for its underwater oil, and protect the environment against spills.

Opponents, who include the major oil companies, say the bill would slow offshore oil production by creating unnecessary new regulation and inviting lawsuits, at a time when a speedup in offshore oil production is needed to reduce dependence on foreign oil.

The House debate was preceded by months of intense lobbying against the bill, and by a three-day blitz of newspaper ads denouncing it.

"If dependence on foreign oil is what you want, H.R. 1614 [the bill] will get it for you," the two-inch-high red letters of one of the ads told readers of yesterdays's issues of The Washington Post.

"If Congress wants to punish the major oil producers through passage of H.R. 1614, then they're spanking the wrong child. In fact, we don't really believe it punishes anybody but the American people," proclaims another ad.

The first ad was paid for by the National Ocean Industries Association, an organization that represents 345 companies, including major oil producers and the drillers, divers, geophysical contractors, food caterers, equipment suppliers, and others who build and maintain oil rigs.

The second ad was paid for by four medium-sized Texas oil companies, the kind of firms the bill's-new bidding procedures are designed to help. One of the companies, Pogo Producing Co., is affiliated with Pennzoil Co.

The others - Diamond Shamrock Oil and Gas Co., Houston Oil & Minerals Corp., and General Crude Oil Co. are large independents or mini-conglomerates; companies that are substantial, but no major, oil producers.

The similarities in tone of the ads, their repetition of major points, and their timing come as no accident.

The ads were a coordinated effort, written and placed by one advertising firm, officials of the organizations involved said yesterday.

"The placing was coordinated through NOIA," said Robert Boylston, head of the Louisiana-based Association of Diving Contractors. The association took a half-paged ad in yesterday's Washington Post.

Ed McGee, a spokesman for the International Association of Drilling Contractors in Houston, said the ads were prepared last September, when it appeared the bill would come up for a vote.

When the vote was delayed, McGee said. "We sort of laid back . . . We all have been in conversation [about the ads] for all that time."

The National Ocean Industries Association and the four Medium-sized oil companies took full-page ads, which cost $11.124. The driller and diver associations bought half-page ads, at a cost of $5,562.