Former Mayor Ray Nagin failed his city “in a time when honest leadership was needed most” and U.S. District Judge Ginger Berrigan should show him no mercy when she sentences him on bribery and other corruption charges next week, federal prosecutors argued in court documents filed Tuesday.

The motion by Assistant U.S. Attorney Matt Coman does not ask for a stiffer sentence than that recommended by federal probation officers in a report to the court.

Although that report is sealed, other court filings suggest that the probation office is recommending a sentence of at least 20 years. Coman says the sentence should be at least as much as the report calls for, “if not higher.”

In 34 pages ticking off every one of the former mayor’s sins, Coman urges Berrigan to give Nagin no quarter. He portrays the former mayor as the mastermind of a corruption scheme involving at least six other players, and says the mayor lied repeatedly to federal agents, to a grand jury, to the news media and to the court over the course of an investigation and trial spanning several years.

The motion documents at least 26 instances in which Coman says Nagin demonstrably lied, ranging from the former mayor’s claim that he never requested that businessman Frank Fradella send him granite for the family business to his denial that he tried to lobby Home Depot for work for that business. Both of those claims were refuted by emails presented at trial. A total of 21 consecutive paragraphs in Coman’s motion begin with the phase “Nagin also lied” or “Nagin further lied.”

If a judge determines that a defendant lied on the witness stand, the “offense level” that controls federal sentencing guidelines is raised by several points — which can mean several years of additional prison time.

Coman also argues that Berrigan should take into consideration several other aggravating factors when imposing Nagin’s punishment. The mayor “eroded the public’s confidence in city government; Nagin committed numerous crimes not out of need or desperation, but out of greed,” he writes.

And his timing was especially bad, Coman argues: “Notably, Nagin committed much of this criminal activity following Hurricane Katrina, when the citizens of the city of New Orleans were in desperate need of honest leadership more than ever.”

Residents of southeastern Louisiana have become inured to corruption, Coman writes, and Berrigan should impose a stiff sentence as a “deterrent” to any other politicians tempted by bribes and kickbacks.

Coman concludes his argument by noting that officials toughened sentencing guidelines for public-corruption offenses in 2004 because of a “national consensus” that such crimes need to be harshly punished. And he lists eight other politicians and businessmen who felt the sting of those new guidelines after they were convicted.

The list includes some locals — businessman Mark St. Pierre, who was among those who bribed Nagin; Benjamin Edwards, a Nagin appointee to the Sewerage & Water Board who took kickbacks from a contractor; and former Gretna City Councilman Jonathan Bolar, who was convicted of extortion. Also on the list are some who made headlines elsewhere: former Illinois Gov. Rod Blagojevich and former Detroit Mayor Kwame Kilpatrick, for instance. All of those named in Coman’s motion got lengthy sentences — the shortest went to Blagojevich, who is serving a 14-year prison term.

Nagin’s lawyer, Robert Jenkins, has asked Berrigan to go easy on Nagin in part because of his lack of a criminal history and his strong familial ties and Christian values.

Nagin’s sentencing hearing is set for 10 a.m. July 9.