The American makers of the drink, Brown-Forman, last week announced a distribution deal with Bacardi Martini, which will see its UK drinks portfolio managed by a new trading company, Bacardi Brown-Forman Brands.
PR work for Southern Comfort was previously handled by Lexis Public Relations.
An agency spokesperson confirmed Lexis had ceased working for the brand as it is continuing to work for Guinness UDV, and the Bacardi deal had thrown up a conflict in client interests.
It is understood that Bacardi Brown-Forman Brands is working with an agency selection firm to produce a shortlist of firms to handle the predominantly consumer PR brief.
Earlier this year, PR work for Brown-Forman's flagship brand, Jack Daniels, was put out to pitch, before being awarded to Freud Communications (PRWeek, 29 March).
No-one at Bacardi Brown-Forman Brands was available for comment, but it is understood that Brown-Forman UK marketing director Sophia Angelis will review the brand's PR handling.
The decision to switch UK distributors has already seen discussions about Brown-Forman's future relationships with its advertising and marketing agencies in the UK.
In September last year Brown-Forman embarked on a £2.5m rebrand of the Southern Comfort range, including redesigning the drink's packaging for the first time in 70 years.