Massachusetts Secretary of State William F. Galvin has charged Prudential Securities with late trading of mutual funds, a practice employed by some in the industry to bolster wealthy hedge fund customers.

The practice has put the mutual fund industry under the microscope in recent months as regulators crack down on tricks used to help the wealthy and the mutual fund companies at the expense of the small investor. According to the complaint, Galvin alleges that brokers in Prudential's Boston office allowed more than 1,100 late trading transactions in the past 2 1/2 years with a total value of more than $162 million.

Galvin charged five former Prudential brokers with fraud last month in a related mutual fund market timing and late trading conspiracy, the Associated Press reported.

"This is yet another example of Wall Street putting the interests of favored clients ahead of retail investors," Galvin said of the charges he brought Thursday. "It's a dismaying but by now a familiar pattern."

The Wall Street Journal reported last week that the Commonwealth's complaint alleges that top Prudential officials knew of the market timing practice and did nothing to stop it.

The Journal reported that Michael Rice, the former president of the private-client division, is alleged to have known that a top-producing group of brokers was using market timing tricks to help clients beat the system at non-Prudential mutual funds.

A Prudential spokesman told the AP that while he had not yet seen the complaint, his company is cooperating with ongoing investigations.