Former budget director Bert Lance is negotiating to sell an undisclosed amount of his 16 per cent interest in the National Bank of Georgia at the premium price of $20 a share, it was announced yesterday.

Lance holds 200,000 shares of NBG, most of which are pledged against a $3.4 million loan from First National Bank of Chicago.

Robert Altman, a Washington attorney representing Lance, made the obligatory announcement of the pending large stock sale but refused to disclose the name of the prospective buyer.

Earlier in the week, Altman informed the Securities and Exchange Commission of the possible sale. The SEC is in the midst of a broad investigation of Lance's bank dealings both at NBG and earlier when he headed Calhoun (Ga.) First National Bank.

Lance paid $17 a share for his NBG stock, which yesterday traded in the range of $10.50 to $11.25. The stock, which has been relatively inactive for several months, gained $1 a share between Wednesday and yesterday, indicating perhaps insider knowledge of the pending Lance sale.

If Lance were able to get $20 a share for all of his NBG holdings - a total of $4 million - it would greatly alleviate his financial woes.

In October, for example, Lance owed an interest payment of about $65,000 just on his Chicago bank loan. The bank would not say whether Lance made this payment.

When Lance revealed his net worth last January before taking the budget job, he showed total liabilities of about $5.3 million. And during the hearings just prior to his resignation, it was revealed that Lance has even more debts than he had declared.

A rough estimate from available figures shows that Lance's debt payments between September and next January will total about $600,000.

Last July, NBG was forced to write down nearly $3 million in problem loans, causing a $1.4 million loss for the second quarter of the year.