Revolutionary changes in the banking and telephone industries brought on by deregulation and fast-changing technology are creating a consumer underclass of poor and elderly Americans who are threatened with the loss of basic services.

Spiraling bank and telephone rates, a fallout of deregulation, have triggered demands for so-called "lifeline" services for millions of low-income Americans. The issue is turning into a major public policy debate over what services are essential for survival in today's technological society.

The lifeline concept was pioneered by utility companies to assure that the poor and elderly continued to receive heat and electricty service in the winter months. With the large customer cost increases, the lifeline concept has spilled over into the banking and telephone industries, where costs to the consumer are expected to double or triple by the end of the decade.

Some critics fear that the bank and telephone lifeline movement is opening a Pandora's box of "essential needs" that will be forever expanding. They are concerned that advocates of lifeline services will try to move into other areas if they win their case with telephones and banks.

Lifeline accounts -- a minimum number of local phone calls at a low price, or a basic, no-frills bank account for a service charge of only a few dollars a month -- have become a key political issue for consumer groups, who are using threats of federal and state legislation to pressure companies to provide free or low-cost services to the poor, elderly and handicapped who they say cannot afford the new, higher rates.

"We hate the term 'lifeline,' " said Kirk G. Willison of the American Bankers Association. "Banking is not a life-and-death situation like a utility service could be."

Lifeline proponents say, however, that access to a phone and bank account have become necessities of life in this modern economy.

"A bank account is essential in society today," said Ken McEldowney, executive director of Consumer Action, a San Francisco-based consumer group. "If you want to rent an apartment, lack of a checking account could be a serious problem. And those without bank accounts are very vulnerable to theft."

"By promoting affordable service for 50 years, we've made the phone an essential element of daily life," said Gene Kimmelman, legislative director of the Consumer Federation of America. "Our decisions about how to respond to emergencies, where to live or how to do business all rely upon efficient, affordable telephone service."

Deregulation has seriously disrupted -- and, in some cases, removed -- a once secure and protective environment for consumers, lifeline supporters say. For example, at a time when the elderly argue that a telephone is more important to them than ever, more than one in five older Americans have been forced to reduce their use of the phone because of higher costs, according to a survey by the American Association of Retired Persons.

"It is important to remember that, in a person's older years, the phone is a necessity, not a convenience," said the AARP's executive director, Cyril F. Brickfield. "It is a vital link to family, friends, social services and even emergency assistance."

There is no evidence yet that the poor are giving up their phones. But lifeline proponents argue that increasing rates soon will force them to do so. Since January 1983, local phone companies have asked state regulators to add $10.9 billion to current local charges, according to a congressional study. The cost of local service is expected to double or triple by 1990, the CFA says.

"The rising cost of rates will force 1.2 million low-income consumers to go without a phone by mid-1985," Kimmelman said. "The $2 billion in 1984 residential rate increases and $1 billion in 1985 access charges will force over 2 milion people -- 60 percent of them below or near the poverty line -- to give up phone service."

Local phone companies defend the higher rates, explaining that they are a result of the breakup of American Telephone & Telegraph Co., the shift from monopoly to competition and the industry's move toward cost-based pricing.

Before deregulation of American Telephone and Telegraph, profits on long-distance phone calls subsidized local rates, according to the telephone industry. Today, AT&T has lowered charges on long-distance calls, but local phone companies -- no longer part of Ma Bell -- are applying for, and getting, big increases in their charge for providing a dial tone.

While the phone companies are not generally opposed to the lifeline concept, they disagree with some of the proposed plans.

Lifeline advocates are lobbying Congress to pass laws that will guarantee discount banking and phone services for low-income persons who can't afford them or, in the case of telephones, to get the Federal Communications Commission to set up a lifeline program. The banking and telephone industries adamantly oppose federal intervention.

The FCC has asked a panel of state regulators and FCC members to make recommendations for local lifeline rates. Lifeline proponents are hoping the FCC will adopt rules later this year requiring states to set up some type of discount rates for local telephone service.

"Access to telephone service has become crucial to full participation in our society and economy," the commission wrote recently.

Supporters of the Lifeline concept don't want to create a politically vulnerable and unwieldy "phone-stamp" program by raising state and federal taxes. Instead, they support federal legislation that would place the financial burden of administering and subsidizing affordable phone service on the phone companies.

One bill, proposed by Reps. Mickey Leland (D-Tex.) and Edward J. Markey (D-Mass.) would require phone companies to subsidize local rates for those least able to afford them, just as phone companies currently pool funds to subsidize service charges in high-cost, mostly-rural areas.

"The Leland/Markey bill would require all telephone users to share the burden of preserving affordable phone service," Kimmelman said.

A similar bill is expected to be proposed shortly in the Senate by Sen. John Heinz (R-Pa.).

Phone companies and state regulators oppose this legislation, however. "The telephone company shouldn't have to bear the expense of lifeline services," said Webb Chamberlain, spokesman for Chesapeake and Potomac Telephone Co. C&P instead has drafted a plan for taxpayer-subsidized telephone lifeline service that is being considered by the Maryland legislature.

Under the C&P proposal, people receiving General Public Assistance or Supplemental Security Income would be allowed to subscribe to a special economy service that would include 30 calls a month for $4.05, half the cost of phone service for regular customers.

The least expensive service now offered by C&P is its economy rate, which costs $5.40 a month, with an additional 9-cent charge for each outgoing call. C&P has proposed raising the cost of the economy service to $9.56 a month.

Lifeline telephone rates are available now or about to be in California, Arkansas, New York and Wisconsin. Lifeline proposals also are pending before several other state utility commissions.

Banks, like telephone companies, are beginning to initiate lifeline services before legislators and regulators do it for them.

The increased competition in the banking industry has greatly expanded services. Financial institutions are able to offer NOW accounts and money market accounts, where savers earn high interest rates, along with bill-payer services, equity loans and more automatic teller machines.

While the new services have enticed wealthy customers, the banks have turned to policies that critics say discriminate against low-income consumers, the elderly and the young to help pay the higher market interest rates.

The proportion of families with checking or NOW accounts fell from 81 to 79 percent from 1977 to 1983, because unprofitable bank branches have been closed in poor neighborhoods and banks are charging more and higher fees on small accounts, said Stephen Brobeck, executive director of CFA.

Banking officials say that they have to set minimum deposit rates and charge for services they once offered for free, because of the costs of maintaining accounts. Banks were once able to offer accounts at no charge because they earned profits through low-interest savings accounts and higher-interest loans. "The more affluent were subsidizing the lower-deposit customers," said Willison of ABA.

Critics point to a Federal Reserve survey, which shows that 20 percent of Americans don't have checking accounts. Poor and lower-middle-income families are forced to cash their paychecks or government checks at check-cashing outlets and to pay their bills by cash or money order, all at considerable expense and inconvenience, Brobeck said.

"As banking consumers, then, they are relegated to the status of second- or third-class citizens," he said. The ABA challenges Brobeck's assertions, however, arguing that its own survey shows that the majority of consumers without checking accounts don't want them.

Bankers also argue that the real problem is that consumers have assumed incorrectly for years that banks provide free services. "Consumers have existed in a state of blissful ignorance in which they never understood that they paid for financial services indirectly with deposits that earned interest at relatively low rates fixed by law," said Howard L. Lax of Trans Data Corp., a financial research firm. "Never having appreciated that they were buying banking services, consumers now do not understand why these services no longer are free."

Nevertheless, the American Bankers Association formed a special consumer task force last month to devise a strategy to tackle the lifeline issue head on. "Consumer advocates could "really become a problem for banks on Capitol Hill this year," a banker was quoted as saying in a recent ABA newsletter.

The fledgling lifeline movement, however, is pushing for federal or state laws to ensure basic banking services throughout the country.

Massachusetts has passed a law requiring all banks to provide free checking and savings accounts to anyone under 18 and over 65 years old. Some lifeline suporters and critics argue that, although the Massachusetts law is a positive step, it has several loopholes. "Some of the most wealthy people I know are over 65 years of age," said James G. Cairns Jr., president of ABA. "Why they should enjoy free banking services is a little hard for me to understand."

One sign that consumer pressures are working is that several banks already have begun to offer basic, no-frills checking accounts.

Security Pacific Bank in Los Angeles, the seventh-largest bank holding company in the country, announced a new "discount banking" account last spring that allows customers who maintain a $100 balance to write up to 10 checks a month for free and have unlimited use of the bank's automated tellers.

A handful of other banks, including Bank of America, are offering similar accounts, and several are considering discount service for low-income people. Willison of ABA said that banks are initiating these accounts because they think the services will be profitable for them.

Security Pacific bankers say they want to start the new account because it's expected to be profitable. The California bank hopes to attract young customers, especially college students, who will be loyal and use other services of Security Pacific when their incomes rise.

"You can't expect a bank to come up with an idea that's socially right, but that it would lose its shirt on," Willison said. "The bank wouldn't stay in business very long.