Fiserv Inc. is suing a former executive of its CheckFree Corp. unit, claiming he is using a confidential customer list to solicit customers on behalf of Charles River Systems Inc.

Daniel Papagni, who was an executive vice president of CheckFree until he was laid off in July 2008, violated a confidentiality agreement and noncompete contract, Fiserv said.

He joined Charles River, of Boston, soon after being laid off and provided it with a customer list and other critical information for its APL portfolio management software platform, the lawsuit charges.

Fiserv, of Brookfield, Wis., routinely requires its employees to sign nonsolicitation, nondisclosure and confidentiality agreements.

The company said that when it acquired CheckFree in 2007, it had all CheckFree employees, including Papagni, reaffirm their confidentiality and nonsolicitation agreements.

Under a severance deal, Papagni received six months' pay and agreed to notify Fiserv if he went to work for a competitor.

"At some time in 2008 or early 2009, in plain violation of his noncompetition obligations to Fiserv, Papagni began work at Charles River as a relationship manager in its New York office," Fiserv said in court papers.

Soon after, the lawsuit charges, Papagni provided Charles River and its sales force with Fiserv's APL client list.

In an attempt to conceal the source of the information, Charles River identified the source of the list on its database as "trade show," the complaint charges.

Fiserv filed the suit Feb. 26 in U.S. District Court for the District of Massachusetts. It is asking for an injunction barring Charles River from using the customer list and for monetary damages.

Charles River, which provides payments software to financial companies, was also named in the suit. Lawyers for the Boston company did not return calls.