Brook, who is the most senior figure to be hit by Channel 4's huge programme of job cuts, also played a major part in the launch of Channel 4's digital channels Film Four and E4.
Channel 4 chief executive Mark Thompson said Brook would continue to contribute to the channel's strategic and creative development through his new business.
"David has made a massive creative contribution to Channel 4 and has been at the heart of some of the Channel's biggest breakthroughs in recent years, from the launch of Film Four and E4 to the brilliant acquisition of Test Match Cricket," said Thompson.
Brook will take a three-month break to study in the US before launching the business, which will help set up a pay TV platform outside the UK. He said being outside of Channel 4 would give him greater opportunity to contribute creatively to its development.
Brook joined Channel 4 in 1997 as director of strategy and development after helping successfully launching Channel 5 with a memorable branding campaign. Brook was awarded Marketer of the Year for his communications campaigns for Channel 4 in 2001/2. Prior to Channel 5 he was marketing director at the Guardian.
According to Brook: "I have been privileged to work with some very talented and creative people at both Channel 4 and Channel Five before that, since I joined the UK TV industry six years ago. But now I want to develop my own business in the wider market place."
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