Bell Pottinger beat four undisclosed agencies to the work, which is understood to be worth six figures.
The BHA is seeking more support from the Government for what it claims is the second largest sport in the country in terms of jobs, attendance and revenues and a significant contributor to UK PLC.
BHA director of public affairs and policy Will Lambe said: "We will be building a compelling case for support across Government, most notably on the improvements required to our funding, and other opportunities around employment, growth and trade.
"This will naturally involve a structured engagement programme across Westminster and beyond, and fully using Racing's network and constituency footprint: the sport plays an integral role to communities nationwide."
The appointment of Bell Pottinger comes after the Labour Party promised to give local councils the power to restrict the business of bookmakers, which Lambe has described as "pivotal to the funding of British racing".
Labour is focused on Fixed Odds Betting Terminals (FOBTs), which have been condemned by critics as the "crack cocaine" of gambling.
Lambe has told The Guardian that "we do not support any measure [to restrict FOBTs] that could compromise their financial viability".