The plaintiff in a proposed class action on Thursday accused high-end retailer Lord & Taylor of negligence in failing to protect its customers' private information, just days after the Hudson's Bay Co. subsidiary announced that it had been the target of a massive data breach in its North American stores.

The lawsuit, filed in the U.S. District Court for the District of Delaware, alleges that Lord & Taylor failed to protect its payment system in the wake of a series of high-profile breaches to hit major retailers in recent years.

According to the complaint, a criminal syndicate known as JokerStash accessed more than 5 million stolen credit cards used at Lord & Taylor and Saks Fifth Avenue stores between March 2017 and late March 2018, with plans to sell customers' sensitive information on the dark web. Hudson's Bay said it had “become aware” of the breach on Sunday, after the cybersecurity firm Gemini Advisory reported it on its blog.

“HBC has identified the issue, and has taken steps to contain it,” Hudson's Bay said in a statement. “Once the company has more clarity around the facts, it will notify customers quickly and will offer those impacted free identity protection services, including credit and web monitoring.”

Bernadette Beekman filed the proposed class action on behalf of all customers who used credit or debit cards at Lord & Taylor stores while the payment system was compromised.

Beekman's attorneys said the proposed class had overpaid Lord & Taylor for privacy protection services that weren't provided and were now forced to spend time and energy monitoring their accounts for fraudulent activity. Lord & Taylor's failure to protect confidential data, they said, had exposed its customers to increased risk of identity theft and fraud in the future.

“The security breach was caused and enabled by Lord & Taylor's knowing violation of its obligations to abide by best practices and industry standards concerning the security of payment systems,” the attorneys said in a 22-page complaint.

“Lord & Taylor failed to comply with security standards and allowed its customers' financial information and other private information to be compromised by cutting corners on security measures that could have prevented or mitigated the security breach that occurred.”

Saks, which is also owned by Hudson's Bay, was not named in the lawsuit.

A representative from the Hudson's Bay press office did not return a call Friday afternoon seeking comment. The firm has said that its customers would not be liable for fraudulent charges resulting from the breach.

The four-count complaint for negligence, breach of implied contract, unjust enrichment and negligence per se is seeking actual and punitive damages, as well as attorney fees and litigation costs.

An online docket-tracking service did not list attorneys for Lord & Taylor on Friday.

Beekman and the proposed class are represented by Janine Pollack and Daniel Tepper of Wolf Haldenstein Adler Freeman & Herz in New York, Ben Barnow and Erich Schork of Barnow and Associates in Chicago and Ralph N. Sianni in Wilmington.

A judge has not yet been assigned to the case.

The case is captioned Beekman v. Lord & Taylor.