It was tough going again yesterday for the Justice Department and the nation's seven regional phone companies, which are urging Judge Harold H. Greene at hearings this week to lift restrictions barring the regionals from new lines of business.

For a second straight day, Greene sharply questioned Justice claims that growing competition and enhanced federal regulation have made the antitrust restrictions governing the phone business obsolete.

Lawyers involved in the proceedings had thought that skepticism expressed by Greene on Monday might ease yesterday because the three-day hearings examining the basic structure of the phone industry shifted focus from the future of long-distance service to the less controversial issue of telephone equipment manufacturing.

If anything, however, Greene yesterday expressed even more doubts about the Justice Department's recommendations in support of the regional companies. At one point, the judge wondered out loud whether the department's benign attitude toward antitrust enforcement arose because it "has taken some Valium and is now relaxed" about the danger of anticompetitive behavior.

Greene retains control over a number of telephone policy issues because he oversees the consent decree that governs the terms of the breakup of American Telephone & Telegraph Co. The judge has been criticized for retaining control over the phone industry three years after the breakup was implemented.

Greene said yesterday that when Justice brought its massive antitrust case against AT&T, and later when the terms of the Bell System's breakup were devised, the department argued vigorously that local telephone companies should be prohibited from using local monopoly power to subsidize their entry into competitive businesses. "Now you say it's not your job. I'm astonished once again," Greene said sharply to a Justice lawyer, Barry Grossman.

The judge's comments may augur poorly for the regional companies, including Bell Atlantic, which serves the Washington area. Justice's decision to reverse its policy and support the regionals in their request to lift the antitrust restrictions appears to have offended Greene, lawyers on all sides of the case agree.

Greene's decision could fundamentally reshape the telephone industry. If he agrees to lift the antitrust restrictions, the regional companies will be free to compete against AT&T, IBM and other giant technology companies in a wide array of businesses.

Those opposed to lifting the restrictions argue that if the regionals are allowed to compete freely, Greene will have created the exact same business structure at the regionals that gave rise to the debilitating public and private antitrust suits filed against AT&T during the 1970s.

"Consumers fear the {regional} companies would impede competition in the equipment markets and drive the price of monopoly phone service higher," Gene Kimmelman, legislative director of the Consumer Federation of America, argued yesterday.

Consumer groups uniformly oppose lifting the restrictions on the regional phone companies, except the restrictions barring entry into information services such as electronic publishing. On that issue, the consumer groups are divided.