The agency was hired by DIC last month to advise on the planned £450m deal, but also provided informal financial PR advice to Liverpool during the deal's early stages.
Brunswick senior partner Susan Gilchrist said that, as DIC's agency, it ‘made sense to help Liverpool out' during initial talks.
She said Brunswick had no official mandate from Liverpool FC and had no plans to provide further advice to the club now DIC had entered an exclusive negotiation period.
Brunswick first worked with DIC when it took over the Tussauds Group in 2005.