Lonegan is claiming the city isn't releasing records regarding his Democratic opponent, Newark Mayor Cory Booker.
Lonegan says the city did not comply with an open records request asking for travel expenses, budgets, audits, and other information for Booker and other city hall employees.
The suit was filed Thursday afternoon in state superior court in Newark.
Lonegan says that Booker is not running a transparent government.
Booker spokesman James Allen says Booker has never used a city credit card or received a reimbursement.
Allen says Lonegan's request includes seven categories of information, including thousands of pages of budgets and audits.