Hertz general counsel Jeffrey Zimmerman has sued a research firm that put the car rental company on a list of businesses "likely to go bankrupt or suffer severe financial distress."

Zimmerman and Hertz have sued Audit Integrity for defamation and trade libel in the Superior Court of New Jersey, where Hertz is based. The suit also seeks undetermined financial damages, a retraction and an apology, and lawyer fees and costs.

The lawsuit stems from an Audit Integrity report that identified Hertz and 19 other large companies as being at risk of bankruptcy.

In response to the report, Zimmerman wrote a letter to Audit Integrity's chief executive, accusing the firm of reaching "incomplete and misleading conclusions".

Zimmerman copied the letter to the GCs of the other 19 companies, including Louis Briskman at CBS, Jennifer Vogel at Continental Airlines, Thomas Cody at Macy's, Patrick Donnelly at Sirius XM Radio and Charles Wunsch at Sprint Nextel. He encouraged the other 19 to join Hertz "in protecting the investing public."

In the letter, Zimmerman questioned Audit Integrity's methods and demanded a retraction. The letter said: "These types of conclusions should not be promoted lightly in a macro environment like the one impacting all of us today. The media is all too eager to republish this disinformation, which harms successful businesses and misleads the investing public."

Hertz said: "The unmistakable assertion disseminated by defendants in their public statements is that Hertz lacks integrity, lies to shareholders and others, engages in fraudulent financial reporting, and is heading for bankruptcy."

Audit Integrity CEO Jack Zwingli said in a statement: "We are disappointed that Hertz has taken this action in an attempt to stifle an opinion they do not agree with. We firmly stand behind our methodology and findings, and will vigorously defend ourselves against this unwarranted litigation."

Hertz's most recent annual report to the Securities & Exchange Commission, filed on 9 March, contains several pages of financial risk factors. In citing more than $11bn (£6.9bn) in debt, the report said: "We have substantial debt and may incur substantial additional debt, which could adversely affect our financial condition, our ability to obtain financing in the future and our ability to react to changes in our business."

However, Zimmerman's letter offered several financial high points for Hertz recently, including a refinancing of $2bn (£1.25bn) in debt one year ahead of schedule.

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