The salacious revelation joins a host of other charges levied against the California Republican, who are not guilty of last year on counts of wire fraud, falsifying records and campaign finance violations.
The filing, submitted as part of a series of motions at California prosecutors on evidence they have used in a trial scheduled to begin in September, provides detailed accounts of five different affairs, including one with a woman who worked in Hunter's congressional office.
According to the filing, Hunter and the unnamed staffer "occasionally spent nights together at his office" and went on dates funded by campaign cash. One night in 201
Prosecutors describe another affair, with a lobbyist, which included a rendezvous at a ski resort near Lake Tahoe in 2010 paid for in large part by campaign funds.
Hunter also went on a double date road trip with the lobbyist and another couple, which included another congressman. He spent $ 905 in campaign funds on a hotel bar tab and the room he shared with the woman, the filing says.
Hunter agreed to step down from his congressional committee assignments when he was first indicted, though he later went on to win reelection, defeating his Democratic opponent After a campaign, it is widely criticized for its anti-Muslim themes.
CNN has reached out to Hunter's congressional office for comment on the affair allegations
Prosecutors also said Monday that Margaret Hunter may testify to her husband's allegedly illegal spending. In a separate file, prosecutors argued that Duncan Hunter could not prevent testimony by claiming spousal privilege if he agreed to waive the privilege himself.
Rep. Hunter has also generated headlines recently for stoking a separate controversy with his forceful defense of Edward "Eddie" Gallagher, a Navy SEAL who is accused of war crimes and who President Donald Trump has reportedly considered granting clemency.
In his defenses of Gallagher, Hunter said he posed for a photo with a dead enemy combatant and later said that as an artillery officer, his unit "probably killed hundreds of civilians."
In an interview with CNN, later clarified that he never targeted civilians but said that those unintended civilian deaths are a consequence of war.
His attorneys thus submitted a series of filings on Monday as part of an ongoing clash over the terms of his September trial.
In one fiery memo, his lawyers called the pretrial publicity "poisonous" and the prosecution's indictment " "and claimed that Hunter, an early supporter of the President, would not receive a fair trial in an area that had voted overwhelmingly for Hillary Clinton in 2016.
They have asked the judge to move the trial from the Southern District of California to the Eastern District of California, which voted for Trump in 2016 – in fact Hunter's defense attorneys pointed out.
His team is also searching for specific charges in the indictment and to limit information related to his financial background because it will prejudice the jury, his attorneys argue.
"It was hard to see how a juror would be predisposed to cast their vote based on their politics," Hunter's legal team wrote.
For their part, prosecutors argued that Hunter's past claims that he is targeted by the "deep state" and the Justice Department in a "witch hunt" could taint a jury pool, and they ask the judge to bring him from submitting evidence about "political bias."
Prosecutors on Monday also asked to admit about Hunter's personal financial circumstances – which lawyers for the congressman pushed back on. In filing, prosecutors provide extensive details of the Hunter family's precarious financial situation, including thousands of dollars in overdraft fees and late mortgage payments.
Prosecutors also included to more potentially scandalous uses of campaign funds by Hunter activity that took place "during get-togethers with his close personal friends" and was "clearly non-work" – but said they would work with his attorneys to avoid public disclosure of it, as it could taint a jury pool.
Both sides are due in court next Monday.