After a former energy client sued Greenberg Traurig for malpractice, alleging it could have avoided millions of dollars in legal fees if not for the firm's negligence, the law firm has shot back, calling the claims purely speculative.

The lawsuit, brought by electrical company NextEra Energy Inc. against the law firm in May, is the latest malpractice suit arising out of bankruptcy actions. Such malpractice claims have been on the rise, according to a report last year by the American Bar Association's Standing Committee on Lawyers' Professional Liability, which showed that bankruptcy was the fifth most common practice for malpractice claims.

The lawsuit by NextEra, formerly known as FPL Group, claims it spent millions of dollars in legal fees, including at trial and for successor counsel at Skadden, Arps, Slate, Meagher & Flom, that it could have avoided if Greenberg, its initial counsel, had asserted a specific defense.