Virginia's top elected state and federal officials agreed yesterday to urge President Carter to help end a ban on new nuclear power plants that they say is costing Virginia consumers millions of dollars a month on their electric bills.

Gov. John N. Dalton said the Nov. 5 moratorium ordered by the U.S. Nuclear Regulatory Commission affected four plants in the nation, including Virginia Electric and Power Co.'s North Anna 2 plant in Louisa County. Dalton said every month that Vepco must buy its power elsewhere costs its customers an additional $12 million on their electric bills.

Dalton and other state officials met with the state's congressional delegation on Capitol Hill and, in a rare display of bipartisan solidarity, drafted a letter to the President saying Vepco has assured them that North Anna 2, a twin to a plant already operating a few hundred feet away, "meets every known safety measure."

The NRC imposed the moratorium as a result of the accident at the Three Mile Island nuclear plant in Pennsylvania earlier this year.

After yesterday's meeting on Capitol Hill, Dalton went to Alexandria. At a press conference there at the city hall, he said: "No one is asking the NRC to take any short cuts or compromise the standards of safety."

Dalton said he is "especially concerned by the apparently illogical situation in which the NRC is allowing North Anna 1 to operate, while delaying operations at North Anna 2." The governor said North Anna 2 "is a virtually identical copy of North Anna 1, which is being refueled after establishing a record as one of the most successful nuclear units in the history of the industry."

North Anna 2 "should be able to operate with equal productivity and safety," the governor said, "for it has the advantages of the most recent safety modifications, including those required by the NRC after its analysis of the Three Mile Island accident."

A spokesman for the NRC said yesterday that Chairman Joseph M. Hendrie and his staff continue to believe that "the prudent course" is to retain the moratorium until the agency has been able to implement all of the recommendations from two studies of the Three Mile Island accident.

Dalton devoted most of his press conference to emphasizing the cost implications, saying the failure of the NRC to license North Anna 2, which could have begun operating in September, "is causing a severe economic hardship for a majority of Virginia's energy customers."

Vepco supplies electric power to 69 percent of the state's population, including heavily-populated Northern Virginia.

Dalton said electricity costs already have increased dramatically because of another NRC decision, to shut down Surry 1, another VEPCO nuclear unit, for a restudy of its ability to withstand earthquakes.

Norman M. Cole Jr., a nuclear engineer who serves as an energy consultant to the governor, produced charts he said showed that NRC's actions affecting Vepco will add more than $100 a year to the bill of an average Northern Virginia customer.

Flanking Dalton at the press conference were Democratic Lt. Gov. Charles S. Robb and Republican Attorney General Marshall Coleman.

Dalton's original draft of the letter to Carter was rejected by Northern Virginia's two liberal Democratic congressmen, Herbert E. Harris II and Joseph L. Fisher, because it called on Carter to overrule the NRC decision. Harris, in a telegram to Dalton, said the president lacks power to intervene in deicsions of the NRC, which is a creature of Congress. Fisher also viewed the original proposal as too harsh. c

A third version of the letter, still being circulated, is considerably milder, merely urging Carter to support Virginia officials in asking the NRC to lift its ban. The final product is expected to be delivered to the White House Sunday or Monday.