Brady demanded that Donovan force HUD's acting inspector general, Michael P. Stephens, to recuse himself from matters involving the city's housing agency, citing his "sour relationship" with the agency's former executive director, Carl R. Greene.
He also sent a similar letter to Stephens, asking him to remove himself from PHA matters.
Spokesmen for HUD and the Inspector General's Office said they would reply directly to Brady before responding publicly to the letters.
Greene was fired by the board last September after commissioners discovered that PHA had secretly settled multiple sexual-harassment claims against him.
Donovan has no authority over the department's independent Inspector General's Office, which is empowered by Congress to detect and prevent waste and fraud.
On March 10, Stephens issued a critical audit of what he called "outrageous fees" paid by PHA to outside lawyers.
The inspector general reported that PHA had failed to give his auditors an adequate accounting of $30 million spent from 2007 to mid-2010 on outside lawyers. He added that in the absence of such an accounting, PHA should have to return those federal funds to HUD.
Brady said the report "was clearly aimed at punishing PHA's residents" for Stephens' bad relationship with Greene. The funds in question, he said, "should be used to provide housing for my constituents," not to satisfy the inspector general's "apparent need for revenge against PHA's former director."
The inspector general's report was "nothing more than an exercise in scapegoating," Brady said.
The HUD Inspector General's Office is independent of HUD itself, noted Jake Weins, an investigator with the Project on Government Oversight, a Washington nonprofit that investigates and exposes government corruption.
"I can't understand why he would write to the secretary," Weins said of Brady's letter to Donovan. "Inspector generals sometimes recuse themselves, but not because secretaries ask them to."
In his letter Thursday, Brady said that as recently as early 2010, Donovan had given high praise to Greene for effectively using more than $125 million in federal stimulus funds to rebuild neighborhoods and create jobs.
To Donovan, Brady wrote: "I hope you will put the same effort toward cleaning your own house as you will direct toward cleaning PHA's. Auditing PHA with an unbiased HUD IG will be a good first step in that process."
Contact staff writer Jennifer Lin at 215-854-5659 or jlin@phillynews.com.