The agency has doubled the number of clients served by its public affairs team in the last three years, the APPC register also reveals.
Under Day, who began his career working for former Conservative shadow ministry David Heathcoat-Amery, the public affairs team has also grown, from eight people in 2014 to 27 people currently advising clients.
Field Consulting, which works with Govia company GTR, continues to work on the account, PRWeek understands.
Other agency wins
Portland, which has the largest number of public affairs staff on the register, with 166, has also grown its client base, with six more clients in the last 12 months.
Among its 54 clients, the agency looks after public affairs for Apple, the Government of Qatar and Nestle.
Westbourne, which has 30 clients and 18 practitioners, has added the Association of British Insurers (ABI) and the British Banking Association (BBA) to its client list in the last year, while Hanover and Cicero have both added one new client each to their rosters.
Nobody from Burson-Marsteller UK was available to comment on the new account wins.