In a move that will further tighten Budget Director Bert Lance's personal financial squeeze, the directors of the National Bank of Georgia today voted unanimously to discontinue the bank's 20 cent quarterly dividened because of recent losses.

Lance was president of the bank until he joined the Carter administration earlier this year and still owns 200,000 shares of NBG stock held in a trust for him.

The bank's dividend has been providing Lance with $160,000 in annual income which he presumably needs to keep up the dept service payments on the $13.4 million loan from the First National Bank of Chicago that is financing his NBG holdings.

That loan - which along with other past and present loans to Lance is being investigated by the Comptroller of the Currency - carries an interest rate of 0.75 per cent over the prime rate, or the rate banks charge their best corporate customers. The prime rate is now 6.75 per cent, so the charge on the loan comes to 7.5 per cent. Annual interest payments at the rate exceed $250,000.

Lance's salary as budget director is $57,500 a year. He has dividend income from other equity holdings - he listed 136 stocks in his portfolio in the financial statement he filed in january - but he has $1.9 million if additional loans, according to the same statement, which he also must service. It is estimated that his total interest charges exceed $400,000 a year.

The balance sheet Lance filed in January listed assets of $7.97 million against debts of $5.34 million for a net worth of 2.62 million.

The assets included $325,000 in cash, $1.3 million in real estate, and $5.65 million in stocks, primarily the NBG shares which accounted for $3.2 million of the total.

Lance now has a loss on paper of about $1 million because of the drop in market price of NBG shares. The rest of the market has not fared well either since the beginning of the year. Lance's current net worth is believed to be closer to $1 million.

In its announcement, NBG said it was discontinuing the dividend "until it is in the best interest of the bank and its shareholders to resume dividend payments," but did not indicate when that might be.

NBG president Robert P. Guyton, who succeeded Lance as chief executive officer, said resumption "depends on the operating performance and results of the bank over the next several quarters," but added he could not "say exactly what would have to take place" in the way of results to make this possible.

The dividend omission had been expected since the bank reported a $1.4 million second-quarter loss that put it into the red for the first six months by $1.25 million or $1.01 a share. The loss was attributed mainly to write-offs of real-estate-related loans totaling $2.8 million in the first half of 1977.

Guyton reiterated today that the extent of the loss so far probably will mean that NBG will report a net loss for all of 1977, and said the bank was "operating profitably," but could face some more write-offs as the year goes along.

As a condition of his confirmation as budget director, Lance volunteered to dispose of his holdings in NBG by the end of 1977 to avoid the potential conflict such a sizeable stake in a bank could present to him in carrying out his government duties.

But the bank's recent earnings problems, coming on top of the prospective sale of Lance's block by a date certain, caused the price of NBG stock, a thinly traded issue, to plummet to as low as $8.50 a share at one point, half of the average price Lance paid.

Lance's trustee, Thomas Mitchell, recently announced he had a probable buyer for Lance's shares. He turned out to be David Smith, an Atlanta businessman, who has said he is willing to pay about what Lance paid for the shares plus accumulated interest on Lance's Chicago loan. But complex negotiations remain before any deal is completed. Meanwhile, it has been disclosed that several other buyers have expressed interest in Lance's holdings, which represent one-sixth of the bank's outstanding stock.

Prior to the announcement by Mitchell, Lance had asked the Senate Governmental Affairs Committee to extend the deadline on his stock sale so he could avoid taking a loss of more than $1 million. At that time, questions were raised about the way Lance obtained his bank financing from the First National Bank of Chicago after it was disclosed that NBG established a correspondent account with the Chicago bank just a month before Lance got his loan.

While the members of the committee lock Lance's word that there was nothing improper in how he obtained the loan, question raised in news reports nonetheless triggered the probe by the comptroller's office into the circumstances of the loan.

That inquiry now has extended into a broad investigation into all of Lance's bank loans and the activities of NBG under his stewardship as well as another Gerogia bank he previously headed, the Calhoun National Bank.

NBG president Guyton said investigators from the comptroller's office hve been here and left after NBG "furnished them with the informationthat they have required." He would not elaborate.