WASHINGTON  Federal officials are bringing far fewer prosecutions as a result of fraudulent stock schemes than they did eight years ago, according to new data, raising further questions about whether the Bush administration has been too lax in policing Wall Street.

Legal and financial experts say that a loosening of enforcement measures, cutbacks in staffing at the Securities and Exchange Commission, and a shift in resources toward terrorism at the F.B.I. have combined to make the federal government something of a paper tiger in investigating securities crimes.

At a time when the financial news is being dominated by the $50 billion Ponzi scheme that Bernard L. Madoff is accused of running, federal officials are on pace this year to bring the fewest prosecutions for securities fraud since at least 1991, according to the data, compiled by a Syracuse University research group using Justice Department figures.

There were 133 prosecutions for securities fraud in the first 11 months of this fiscal year. That is down from 437 cases in 2000 and from a high of 513 cases in 2002, when Wall Street scandals from Enron to WorldCom led to a crackdown on corporate crime, the data showed.