A threatened boycott of Maryland National Bank for moving its credit card division to Delaware could cause problems for the bank and its parent, Maryland National Corp.

On the other hand, the boycott being advocated by a group of ministers in the Baltimore area could turn out to be just another quixotic gesture.

In any event, Maryland National is in "sort of a no-win situation," observed spokesman Dan Finney.

The region's largest banking institution has become the first Maryland bank to carry out plans announced some time ago to move its credit card operations to Delaware. The state's other major banking institutions are expected to ship similar operations across the border by late spring or early summer.

Several Maryland banks threatened to move their credit operations to Delaware if the Maryland legislature failed to allow annual credit card fees and higher interest charges on consumer purchases.

Delaware, which has no interest-rate ceilings or restrictions on credit card fees, has become increasingly attractive as a base for credit divisions of out-of-state banks.

While Maryland's General Assembly, under heavy pressure from the banking industry, is trying to find an acceptable face-saving solution to the question of deregulating interest rates, Maryland National already has established a credit card subsidiary in Delaware.

What's more, Maryland National has advised holders of its MasterCard that if they use it after March 15, they will have to pay an annual fee of $18. Also, the finance charge on monthly purchases will increase to 18.9 percent annually.

Currently, Maryland law permits an annual percentage rate of 18 percent on the first $700 of credit purchases and 12 percent on amounts above that. The legislature is considering a bill that would allow an interest-rate ceiling of 24 percent on credit card purchases and most consumer loans.

Equitable Bank hasn't yet received final approval from Delaware authorities but expects to move its MasterCard and Visa operations to Delaware by July, said Barbara Lucas, a vice president at Equitable Bancorporation.

First Maryland Bank is expected to inform its cardholders next month of plans to charge a fee following the shift to Delaware.

"It's an economic necessity," Lucas said, reflecting a consensus in the state's banking industry. "We've all experienced losses in this credit card portfolio because of the constraints of operating under Maryland law."

While Lucas declined to give a dollar-loss figure for Equitable, Finney said Maryland National lost $7.2 million last year on its credit card operations. Maryland's bankers association reported that the five biggest banks lost more than $18 million on credit card operations last year.

Finney maintains that 18.9 percent is reasonable, considering the prevailing ceiling in Maryland. Moreover, he noted, the average balance of the 301,000 active Maryland National accounts (it has a base of 350,000) is $555.09, meaning that most persons already pay 18 percent in interest annually.

But the key to profitability is the annual card fee that Maryland banks will be able to charge for the first time.

The chief advocate of a boycott of Maryland National points to higher overall bank earnings and suggests the claims of losses on credit card operations are false.

"It's greed," contends the Rev. William E. Johnson, president of the Baptist Ministers Conference of Baltimore and Vicinity.

Johnson said the moves to Delaware are the banks' way of "putting the squeeze on the legislature" to win deregulation of interest rates. "They're moving like a child running away from home because he can't have his way," Johnson allowed.

Although his group claims to represent about 113,000 parishioners, Johnson maintains it has "tremendous support" from "all races and denominations."

Johnson has urged Maryland National to reverse its decision and has called for a meeting with bank officials. A representative of Maryland National will meet with Johnson, but a reversal at this point is wishful thinking.

Maryland National already has hired 170 full-time and 50 part-time employes to work at its Delaware subsidiary. Employes who worked in the bank's old credit card department have been transferred to other positions in the bank, diffusing charges that jobs will be lost in the move.

The same procedure will be followed by Equitable. In fact, about 50 Delaware residents who have been hired to work in Equitable's new subsidiary are bused daily to Maryland and back for training.

Although the die is cast, Johnson is confident his organization has sufficient support to pressure the banks into changing their plans.

Johnson said his organization and supporters are trying to persuade people to return their MasterCards to Maryland National. Moreover, he warns, churches, labor unions and individuals will be asked to "take their accounts held by Maryland National and negotiate elsewhere."

But with most, if not all, major Maryland banks planning to move their credit card operations, who will be left to negotiate? Johnson says there are enough smaller banks who can use the business.