The agency confirmed that it had started consultations with five staff.
H&K declined to comment further, but the cuts are believed to be in the agency's corporate practice, triggered by the loss of key accounts.
The WPP-owned consultancy recently lost a contract with the Learning and Skills Council, but will continue its consumer work. Zurich Financial Services last week moved its retained UK corporate media relations account to Fishburn Hedges, though the agency retains Zurich's global corporate PR account.
WPP sister agencies Ogilvy and Cohn & Wolfe have already cut jobs this year.