Federal regulators assured a Senate panel yesterday that they would intensify their surveillance over banks as a result of allegations of questionable activities by some bankers.

The regulators testified before the Senate Banking Committee, which is reviewing the results of a survey of bankers conducted by the three regulatory agencies - the Federal Reserve System, Federal Deposit Insurance Corp.; and Office of the Comptroller of the Currency.

The survey sought information on bank stock loans, insider loans, overdrafts, and loans to officials and major stockholders of other banks.

The report was requested by Committee Chairman William Proxmire (D-Wis.) last September after Bert Lance resigned as budget director following allegations of his questionable banking practices when he headed two banks in Georgia.

While Proxmire viewed the survey as confirming his often voiced criticisms of bankers and banking practices, the regulators voied reservations about the survey's conclusions.

J. Charles Partee, a governor of the Federal Reserve Board, said, "In general, while the results raise questions about potential insider abuses, these dubious practices do not appear to be widespread or to involve quantitatively large commitments of available funds."

George A. LeMaistre, chairman of the Federal Deposit Insurance Corp., said, "Although overdrafts are permitted by a large percentage of banks, abuse or violations of law are not widespread."

The survey, made public a few weeks ago, concluded among other things that about 30 per cent of the banks that responded granted interest-free overdrafts of more than $1,000 to insiders during the first nine months of 1977.

Comptroller of the Currency John G. Heimann said, as a result of the survey, "I have directed the staff to review systematically our approach to insider abuse in order to determine what should be strengthened and what should be discarded."

Sen. Thomas H. McIntyre (D-N.H.) criticized the expense of the survey, which he estimated cost banks and the government about $3.5 million.

Many bankers could not understand the questions in the survey. LeMaistre testified that the Federal Reserve "made over 10,000 (phone) calls to banks to edit their reports."

All three regulators endorsed the Senate-passed legislation on bank reforms. That version has also been endorsed by the American Bankers Association, but it remains stalled in the House Subcommittee on Financial Institutions. The subcommittee chairman, Fernand St. Germain (D-R.I.), wants a much tougher bill.