Joe Khan, a former federal prosecutor challenging Philadelphia District Attorney Seth Williams in the 2017 Democratic primary, on Thursday called on Williams to release his federal tax returns.

Khan, standing in front of the local IRS office in Center City, said he was "outraged" that Williams has refused to answer questions from the media about amending in August his statements of financial interests from 2010 to 2015 to disclose $160,050 in previously unreported gifts.

Khan said those disclosures "raised more questions than they answered," including if Williams met his federal tax obligations for the gifts.

Khan then gave journalists copies of his 2015 and 2014 federal tax returns while calling on Williams to do the same.

"You can't be a candidate for district attorney, let alone be the district attorney, while running from reporters and refusing to answer questions about your own conduct," he said. "If my opponent wants to keep hiding from the cameras and the microphones, the very least he could do as a public official is to give the press his federal tax returns."

Williams, while hosting a campaign fund-raiser at a Center City cigar bar Thursday, declined to comment and referred questions to Dan Fee, a spokesman for his campaign.

Fee, in an email, said Williams was focused on his job and participates in dozens of meetings and public events, including speaking with media outlets.

"But what he has not done is begin to focus on his campaign," Fee said. "When he does, he will respond to things other candidates say about him."

Williams in August took responsibility - slowly - for his failure to disclose the $160,050 in gifts.

He first issued a statement painting the disclosures as "intended to demonstrate transparency."

He followed up a few days later in an email to his employees, apologizing for the "adverse publicity" the disclosures drew.

A week after the disclosures, with public criticism about the gifts growing, Williams' campaign emailed supporters a statement in which he said he "takes full responsibility on failing to disclose what was required."

Khan, who left his job at the U.S. Attorney's Office in Philadelphia in September to enter the race, on Thursday noted that Williams' finances were under federal investigation.

The Inquirer in August 2015 reported that the FBI and IRS, working with a federal grand jury, issued subpoenas for records from the political action committee Williams used to run for public office.

The Second Chance Foundation, a nonprofit Williams founded in 2011, received a federal subpoena for financial documents in August.

215-854-5973 @ByChrisBrennan