The appointments, which include Simon Bielby, a business director at MindShare, will make the team more than 60 strong.
Bielby, a strategic planner on MindShare's Nestle business, is joined by communications strategist Bruno Martin, previously at econometrics specialist Point Logic and Saatchi & Saatchi.
Other hirings include former Optimedia and Media Planning Group communications planner Ian Turnbull and Josh Howdle Fuller, previously a media strategist at Walker Media.
Initiative has also boosted its consumer insight strength with the appointment of Jane Anthony, research manager at Camelot, and Jessica Lowen, who joins from Viacom as a strategic researcher.
The agency recently lost a senior member of its communications planning team when creative director Lucy Banks resigned to join ZenithOptimedia in a similar role.
Tony Manwaring, communications planning director at Initiative, said: "One of the challenges faced by the industry is to offer credible strategic advice that is relevant and of sufficient scale to deliver accountable results for our clients. It is all too easy to equate 'strategic' with 'media-stunt' and that is not what we are about."
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