Bell Atlantic Corp., parent of Chesapeake & Potomac Telephone Co., last week joined another regional telephone company in publicly asking the Department of Justice to allow the companies to offer new services.

Court decisions imposed during the breakup of the Bell System currently restrict the companies from manufacturing equipment, providing long-distance telephone service and offering information services, such as data processing.

U.S. District Judge Harold H. Greene, who presided over the breakup of the Bell System, and the Justice Department are not expected to review the relaxation of restrictions until 1987.

Thomas E. Bolger, chairman of the company, told analysts in New York last week that Bell Atlantic should be free to compete in areas now out of reach because of a new competitive threat from American Telephone & Telegraph Co. for the largest business customers of the phone companies.

"The primary reason for the breakup of the Bell System was to stimulate more competition in the telecommunications industry," said Bolger.

"That competition will not take place until Bell Atlantic and the other regional telephone companies are relieved of restrictions that now inhibit, rather than facilitate, the development of true and fair competition," he said.

The Federal Communications Commission has "legalized" bypass of the local phone networks by allowing AT&T to connect its lines directly to large businesses, he said. But, in its present form, the decision, to which the regional phone companies are bound, creates a regulatory "security blanket" for AT&T, while severely restricting Bell Atlantic's ability to compete successfully in the marketplace, he said.

Bell Atlantic followed Ameritech, a regional phone company based in Chicago, in asking for a reconsideration by the Justice Department.

Behind the scenes, all the companies have lobbied Capitol Hill aggressively in recent months to get restrictions relaxed. Two bills have been introduced so far that would allow the companies to provide information services or to manufacture equipment.

Meanwhile, last week the Justice Department said it had asked the U.S. District Court to make existing procedures simpler. Justice recommends which new lines of business the phone companies can enter, from real estate to overseas telecommuncations consulting. Judge Greene has final say over giving the companies permission to enter the new businesses.

Under the new Justice Department proposal, telephone companies would be able to join any other pending request by another Bell company in asking for the right to pursue new business lines.

A company joining a request would be bound by identical terms and conditions contained in the request entered on behalf of the original applicant.