James Spertus told the Los Angeles Times Thursday that Bell agreed to pay Rizzo back pay and a severance package when he resigned in July.
Rizzo and seven other city officials have been charged with corruption.
Spertus says the city is violating state labor laws by not paying up.
Rizzo also has asked the city to pay his legal bills.
Bell's acting city attorney, Jamie Casso, says he can't comment on Spertus' claims, because it is a personnel matter.
Rizzo was one of the highest-paid municipal officials in the country when a Times investigation revealed that he would have earned more than $1.5 million in compensation this year.