Attorney General Martha Coakley is suing Lawrence Mayor William Lantigua for allegedly breaking the state's campaign finance laws.
Those allegations include accepting thousands in possibly illegal cash and corporate contributions.
The complaint alleges Lantigua's campaign accepted more than $14,000 in 2009 in potentially illegal cash contributions as well as failing to report potentially illegal contributions in the form of advertisements.
The complaint also alleges Lantigua failed to report nearly $20,000 in expenditures during 2009.
The lawsuit was filed in Suffolk Superior Court on Tuesday by Coakley and the Office of Campaign and Political Finance, which referred the case to her office last year.
A message left at Lantigua's office was not immediately returned.
In January, Coakley sued Lantigua for failing to file a 2011 campaign finance report. Lantigua paid a $5,000 fine and filed the report.
