Attorneys for former Virginia governor Robert F. McDonnell want federal prosecutors to be more specific about the “official actions” they allege he performed for a wealthy Richmond area businessman in exchange for loans and expensive gifts.

In a motion filed Thursday in U.S. District Court in Richmond, the lawyers asked prosecutors to produce a “bill of particulars” adding more detail to their 14-count, 43-page indictment that accuses McDonnell (R) and his wife of corruption while he was governor. The motion says the indictment, although “unnecessarily detailed in some respects,” falls short in defining the “official actions” that McDonnell allegedly performed or promised to perform for Richmond businessman Jonnie R. Williams Sr.

To prove the corruption ­charges, the government must show that the couple performed official acts to benefit Williams. “If the Government is unable to allege — or prove — that Mr. McDonnell performed or promised to perform any action which qualifies as an ‘official action,’ then its corruption charges fail as a matter of law,” McDonnell’s attorneys argue in the motion.

The McDonnells have pleaded not guilty to the charges, and a trial is scheduled for July 28.

The motion is the latest in a string of filings attacking the government’s case and accusing prosecutors of failing to properly turn over evidence to the defense. It repeats many of the points that the couple’s attorneys have made previously and offers another window into the defense’s strategy: that whatever McDonnell did for Williams would not qualify as an “official” action.

Legal experts have said proving the allegation in court could be difficult.

Prosecutors have accused McDonnell and his wife, Maureen, of lending the prestige of the governor’s office to Williams and his struggling company, Star Scientific, a former discount cigarette manufacturer that now sells dietary supplements. In exchange, they allegedly received loans and gifts of money, clothes, golf fees and equipment, trips and private plane rides. The gifts and loans totaled at least $165,000.

Prosecutors say Robert McDonnell hosted a product launch for Star’s dietary supplement, Anatabloc; promoted it at public events; arranged meetings between Williams and senior state health officials; and worked with his wife to encourage state researchers to consider conducting trials of the product.

Williams stepped down as Star’s chief executive in December.

The defense’s latest motion asks the court to order prosecutors to produce more specificity on all of those accusations. It also asks the court to order prosecutors to identify others who they allege conspired with the McDonnells, saying those people’s names are critical to the couple’s defense.

“Knowing who these people are is especially important in this case because many critical witnesses — including almost everyone who worked for the McDonnells while Mr. McDonnell was the Governor of Virginia — are represented by counsel and have been reluctant to speak with the defense, possibly because they are afraid of likewise facing federal charges,” defense attorneys argue in the motion. “Requiring the Government to clarify which people it actually believes were involved in the alleged conspiracy would dissipate that cloud of concern.”

As of Friday evening, prosecutors had yet to respond to the filing, and a judge had not ruled. Defense attorneys requested a hearing on the matter.