WASHINGTON — A year after an internal whistleblower accused the Securities and Exchange Commission of improperly destroying records of dropped enforcement inquiries, the agency is still destroying records illegally, a lawyer for the whistleblower said in a letter Tuesday.

The whistleblower, SEC staffer Darcy Flynn, is under “standing orders to direct the destruction of records” that federal law requires the SEC to preserve, attorney Gary Aguirre wrote. Aguirre’s letter suggests that the destruction of documents has been wider than previously alleged.

The SEC should halt “ the current practice of destroying documents after the completion of a formal or informal investigation” until the National Archives has approved the process, Aguirre wrote.

Aguirre has argued that the destruction of SEC enforcement records could make it harder to hold the agency accountable when its staff decides not to fully investigate allegations of Wall Street wrongdoing or take action against alleged wrongdoers.

Documents still being destroyed are “internal work product” generated by the SEC’s enforcement staff, Aguirre wrote.

His latest allegation contrasts with an assurance the SEC gave last year after Flynn told the National Archives that the agency was destroying investigative records without authorization.

In an Aug. 27, 2010, letter, the SEC told the National Archives that it had instructed its staff to preserve the records in question, which are those pertaining to so-called MUIs, or “matters under inquiry,” an early stage in the investigative process, while it tried to sort out the issue.

When Flynn’s original allegations were made public last month, an SEC spokesman confirmed that for years the agency had directed its staff to dispose of records obtained in connection with MUIs if the agency decided to close those inquiries without a full-fledged investigation.

But the SEC spokesman, John Nester, said the agency changed that policy last year.

In his letter Tuesday, Aguirre said SEC Chairman Mary Schapiro “may be responsible for some of the current violations.”

An SEC spokesman did not immediately respond to a request for comment.