U.S. banks earned a record $25.3 billion last year, the government reports, but a top regulator chided the industry for passing on more than half the profits to stockholders and advised banks to adopt a more conservative approach.

Federal Deposit Insurance Corp. Chairman L. William Seidman, previewing a report to be issued by his agency on Tuesday, said bank profits for the three months ending Dec. 31 hit $6.7 billion, an all-time high and $800 million more than the previous record of $5.9 billion set in the third quarter."This is the first time we have ever seen consecutive record-setting quarters," he said in a speech prepared for delivery to the New York Society of Securities Analysts.

The U.S. economy, as measured by the gross national product, last year expanded at the fastest pace in four years, and banks' business expanded along with it. Also, Third World loan problems, which forced banks to take big losses in 1987, improved somewhat last year.

For all of 1988, the nation's 13,200 commercial banks earned $25.3 billion, up from $3.7 billion in 1987 and topping the previous high of $18.1 billion, set in 1985.