The White House said yesterday budget director Bert Lance was unaware that he had pledged the same block of stock as collateral for personal loans he received from two New York banks in 1975 and 1976.

Press secretary Jody Powell thrown suddenly on the defensive by another revelation involving Lance's complex personal financial dealings, spent most of the day trying to sort out the details of the transactions.

By the end of the day, he said he was satisfied that Lance had actual ethically in handing the twa loan and that the double pledge of the same collateral did not reflect on the competence of the nation's budget director.

Details of the transaction, buried deep in the report of the comptroller of the currency that was released last week, were first reported yesterday by Associated Press. When first confronted with the finding that he had used the same collateral to secure two separate loans, Powell said. Lance refused to believe he had done such a thing.

But the White House did not dispute any of the facts involved in the transactions. Instead Powell defended Lance by arguing that there is no reason to believe that Lance deliberately violated a loan agreement with one bank in order to obtain a second loan from another.

According to the comptroller's report, this is what was involved in the two loans.

In June, 1975, Lance obtained a $2,625 million loan from Manufacturer's Hanover Trust Co. of New York. Lance used the loan to gain a controlling interest in the National Bank of Georgia. Part of the loan was 179,000 stares of NBG stock that he had purchased with the borrowed money.

The loan agreement included a stipulation that Lance would also turn over to Manufacturers Hanover any dividends from the NBG stock as additional collateral.

Late in 1975, Lance received such a dividend in the form of 14,657 additional shares of NBG's tock. But he did not, as required by the agreement, turn that stock over to Manufacturers Hanover. Instead, in February, 1976, he used the 14,657 shares as collateral to obtain a $150,000 personal loan from Chemical Bank of New York.

In June, 1976, according to the comptroller's report, Manufacturers Hanover began prodding Lance about the collateral for the $2,625 million loan. In a letter dated June 2, 1976, R. Bruce Brougham, a vice president of the bank, referred to "the current undercollateralized position" of the loan and told Lance "as I understand it, you will bring the additional shares of NBG stock you were issued as a stock dividend at year end."

In another letter, dated Nov. 5, 1976, Betsy Jo Viener, a Manufacturers Hanover vice president told Lance: "We still have not received the 14.657 shares which you were issued as a stock dividend as of 12/31/75 . . ."

One reason the bank was seeking additional shares of stock as collateral was that the value of NBG stock kahad declined since the loan was issued. Thus the loan, at this point, was undercollateralized.

Powell yesterday characterized this correspondence about the additional 14,657 share of NBG stock as "in the nature of negotiations" with the bank seeking additional collateral and Lance attempting to keep the amount of collateral "at the lowest possible level."

He said it was not clear to him whether during this period Lance realized the full terms of his loan agreement with, Manufacturers Hanover, under which he ahd a contractual agreement to surrender the stock to the bank.

The press secretary also argued that Lance had "unwittingly" pledged that same stock to Chemical Bank. There was no reason for Lance deliberately to make a double pledge of the same stock, Powell asserted, because Lance had plenty of other unencumbered assets he could have used to obtain the $150,000 loan from Chemical.

But when pressed on this point, Powell conceded that he had checked only on whether Lance did have other assets available at this time, and not on the extent or strength of those assets.

Yesterday's revelations about the double pledge of collateral produced what was probably Powell's most uncomfortable day in his role as the leading administraton defender of the budget director. He was forced to hold two separate briefings on the Lance matter, and to fend off numerous questions about the ethics involved in the transactions.

Since release of the comptroller's report, which cleared Lance of violating banking laws or regulations, President Carter, Powell and others have said repeatedly that Lance has not been guilty of anything "illegal or even unethical." Powell has challenged reporters to cite instances in which Lance acted unethically.

At his regular morning briefing, Powell was asked whether he considered Lance's use of the same stock to obtain two loans to be unethical. "Based on what I know about it, on," he responded such as practice if he considered such a practice to be proper and ethical, he replied, "Of course not."

Visibly discomforted by the questions of ethics, Powell told reporters: "I don't and neither does the President or Mr. Lance, endorse practice of overdrawing your bank account" (for which Lance was criticized by the comptroller).

"Whether that is a question that at-unfit to serve in public office is some-tasks a man's ethics and makes him.

Powell called reporters back to the thing else."

White House late yesterday to offer his explanation that Lance was unaware of the details of his loan agreement with Manufacturers Hanover when he pledged the stock as collateral to Chemical.

Asked again if he is convinced that Lance had acted ethically, Powell said, "Yes, I am." But he conceded that the question of how Lance responded to Manufacturers Hanover's requests for the additional stock as collateral - something that is not addressed in the comptroller's report - "will have to be dealt with."

"It would be appropriate not to make a hasty judgement," the press secretary said.

Powell also said that at a breakfast meeting with reporters on Thursday he had not meant to give the impression that White House aides had seriously discussed the possibility of asking Lance to resign.

Powell said Thursday that he and other senior White House aides had discussed the possibility of a Lance resignation "at some length." Yesterday he said those discussions involved only agreement among White House officials that they could not "in good conscience" consider such a course of action.

"There was never any lengthy discussion of asking Bert Lance to resign," Powell said.