The COI's long-standing PR and client director Oliver Hickson has left the organisation after 15 years, as part of a wide-ranging redundancy programme.
In addition to Hickson, the head of the COI's PR framework Jo Dixon left last week, also taking redundancy.
The news comes as the COI waits to find out whether it will be axed as part of the Cabinet Office public bodies review.
Other departures from the COI include seven members of the live events division, following a department-wide jobs cull of 287 employees. This comes at the end of a 90-day consultation period.
Hickson joined the COI in 1995 and in his final role there looked after all PR agency, best practice, evaluation, education and armed forces PR work. He left the Government body on Monday, to commence work as a freelancer.
He said: 'I'll be working in consultancy in PR and sponsorship, around areas such as best practice. It's been a fantastic time at the COI but I'm really looking forward to using all my experience and skills within the wider PR and sponsorship industries.'
Once the review of government advertising announced by the Cabinet Office in October is complete, further announcements are expected on the COI's future role, remit and structure.
A COI spokeswoman said: 'The COI is now coming to the end of the redundancy consultation we announced in August, which was designed to reduce headcount by 40 per cent.'
How I see it
Mike Granatt, Director, Luther Pendragon
For more than 30 years, governments all over Europe envied and then emulated the COI.
They also wanted an expert agency that used buying power and experience to save taxpayers tens of millions a year, and to grab critical slots at short notice.
They saw the value of an unimpeachable buying process that protected ministers from accusations of buying politically advantageous advertising and media from 'friends'.
And they understood the value of rosters that protected ministries from tortuous European procurement procedures.
Let us hope the British Government doesn't forget why it set up the COI when it gets interested in mass communication again - probably not long before the next election.