Cooper is returning to the company he founded, Populus, tomorrow after a two-year leave of absence working for Cameron.
His departure comes as the Tories focus on turning strategy into votes in the long build-up to the 2015 general election, and was described as a sign that the party was now focusing on implementation under election strategist Lynton Crosby, who joined in November last year.
Chris Wilkins, Populus planning director, said: "Andrew went in to help set up for the Government’s narrative with a view to the next election and he feels he has done that. The story is now more on the implementation, which Lynton has been brought in to do."
At Populus Cooper will help clients in the corporate, political and charitable sectors develop evidence-based comms strategies and campaigns.
This will include Number 10, with Cooper continuing to offer advice to the Prime Minister and overseeing data analytics for the Conservatives' election campaign.
Cooper said: "It has been a fascinating experience to work at the heart of government. I look forward to continuing to support and advise David Cameron in the run-up to the 2015 election, but I am also looking forward to the challenge of bringing the increasingly sophisticated techniques of political research and analytics to the corporate world in order to help clients address their strategic and communications needs."
Cameron laid out his party's agenda with a conference speech hinting at further reforms of the welfare system and a pledge to "keep on cutting the taxes of hard-working people in our country".