Bulleit bourbon has been a big winner for Diageo and a prime example of how a liquor giant can grow a niche brand without sacrificing its craft-like independent spirit. Now the fast-growing brand is on the attack against a competitor that Diageo says is trying to steal some of Bulleit's frontier vibe.

In a lawsuit filed this week in federal court, Diageo alleges the smaller Redemption bourbon brand committed trademark infringement by copying the vintage style of Bulleit's packaging and branding. Diageo stated that similarities included the clear canteen-shaped bottle with rounded shoulders and embossed brand name above the label. The lawsuit also points to branding that referred to Redemption as a "saloon era" and "pre-prohibition" whiskey. Bulleit is marketed as a "frontier whiskey" whose packaging is meant to "evoke the rugged look and feel of the American Frontier," according to the lawsuit.

Redemption was previously sold in cylinder-shaped bottles with a more modern look, according to the suit. Diageo alleges that Redemption was revised to mimic Bulleit after the brand was acquired by Deutsch Family Wine & Spirits, a wine and spirits marketers whose brands include Yellow Tail. Deutsch bought Redemption from Bardstown Barrel Selections in 2015.

Diageo's lawsuit is "devoid of any merit whatsoever," Deutsch Family Wine & Spirits President Tom Steffanci said in a statement. "The packaging for Redemption was thoughtfully designed to reflect and highlight a lawful trademark and to differentiate this whiskey. We will not only vigorously oppose Diageo's lawsuit, but we will also continue to defend the integrity of the Redemption brand against any unfair linkage and/or association with Bulleit, or any other competitive product."

Diageo has already exacted some concessions in a similar case against Sazerac, whose brands include Southern Comfort, Fireball and Buffalo Trace. In a suit filed last year, Diageo alleged that bottles of Sazerac's Dr. McGillicuddy's brand mimicked Bulleit's look. The companies reached a settlement. A Diageo spokeswoman said the deal included an agreement by Sazerac to "modify the packaging of their McGillicuddy's flavored and Irish whisky products going forward." A Sazerac spokeswoman said "we do not comment on litigation matters."

Diageo's legal aggression is a sign of the rising importance of Bulleit in its vast spirits portfolio. The brand grew dollar sales at stores by 17.8% in the 52 weeks ending May 14 to $47.6 million, according to IRI. That ranks it 12th among whiskeys, one spot behind Diageo sibling brand Johnnie Walker, whose sales fell 4.3% to $62.2 million. Diageo's top-selling whiskey is Crown Royal, the second-ranked whiskey by store sales at $269.5 million, according to IRI. Brown-Forman's Jack Daniel's is No. 1 at $307.5 million.