In their mayoral primary debate, Avella mentioned the state pension fund scandal and Thompson's donations from money managers - then asked Thompson if he has been questioned by the FBI, the Securities and Exchange Commission or the attorney general.
"Absolutely not," Thompson sputtered. "New York City has not been touched by those scandals."
It's true that Attorney General Andrew Cuomo's probe of dirty pension fund dealings has not made any headlines about the five funds Thompson manages.
"As the controller has consistently noted, he reached out from the start to the AG's office to assist in any way," said Thompson spokesman Jeff Simmons. "We have not been and are not the subject of the state's investigation."
Avella's question was designed to raise seeds of doubt, though - and he followed up by telling reporters afterward he had his ethical doubts about Thompson.
"There's some real serious issues here, and I don't think we've heard the last of it," Avella said. "Before I say I'm going to endorse him if he wins the primary, I want to make sure that there isn't an indictment coming down the road."
Thompson has been unscathed so far by the scandal that exploded in March, when Cuomo charged Democratic power broker Hank Morris with taking kickbacks from companies that won pension investments.
A Cuomo spokesman did not return a call for comment, but Democrats know the issue is out there - because some of the companies named in Cuomo's probe are involved in city pension business as well.
The founder of pension adviser Aldus Equity was charged in April with paying Morris a kickback in exchange for getting state pension investments, for example - and Aldus got a $500,000 consulting fee from the NYPD pension fund last year.
Not that it's easy to tell whether anything unseemly is at work.
Go to the Web site of the state controller, Tom DiNapoli. In two clicks, you can see monthly reports of new pension investments and whether any middlemen got fees.
DiNapoli also posts quarterly updates of the fund's performance, and files a quarterly list of fund investments with the SEC in Washington.
Thompson? Poke around deep enough into his Web site and eventually you'll find links to four of the pension funds (the FDNY fund isn't even online). You can find annual performance results for them, and an annual list of who gets the money - months after the fact.
It's a lackluster technological showing, especially when Thompson is running against the guy who set up 311.
To be clear, nobody has accused Thompson of wrongdoing. And as Thompson points out, Mayor Bloomberg's appointees chair or co-chair all five of the pension funds.
But Thompson is the one who runs the office in charge of investing in those funds. And as long as Cuomo is looking at pensions, the questions Avella asked last week will keep echoing.