The move is part of a 'comprehensive strategic review' following the merger of the holding companies in May, led by executive chairman Lord Chadlington.
The combined business will trade under the GCG brand, with the CPA name likely to be scrapped some time next year. The merger aims to create a 'powerhouse covering the US and the European Union'.
It will bring together GCG's eight offices, dominated by a strong presence across the US, and CPA's offices in London, Brussels and Edinburgh. However, the deal does not affect Huntsworth's other significant PA business, Grayling Political Strategy.
GCG operates PA, corporate comms and investor relations divisions - 45 of its 110 staff work in public affairs. CPA employs 35 staff across its three offices. Incepta bought the lobbying consultancy in 1987, known then as Westminster Communications, which it rebranded as Citigate Westminster and then Citigate Public Affairs in 1999. CPA chairman and chief executive Warwick Smith becomes a vice-chairman of the combined entity, alongside GCG's Jeremy Kane. The pair now report to GCG's New York-based public affairs chief Geraldine Ferraro.
GCG's Stephanie Lvovich has been made MD of the combined EU public affairs offer in Brussels. Her hire follows Thierry Lebaux's departure as head of CPA's EU office for Edelman, where he will be vice-chairman of PA. Smith said there was a 'natural logic' to the merger, adding it would 'come together under the single brand' in nine to 18 months' time. The London offices will be brought together.
GCG and CPA have a combined fee income of around $28m (£16m), with CPA accounting for £3m.