Cooper rejoins Populus “in a new role helping clients in the corporate, political and charitable sectors develop evidence-based communication strategies and campaigns”, according to the firm.

He was deputy director of research for Cameron’s party, the Conservatives, from 1996 through the 1997 general election, after which he became director of strategy, a position he held until setting up Populus in 2003 with another party colleague Michael Simmonds.

Cooper took a leave of absence from Populus in February 2011 to work for Cameron in 10 Downing Street.

Despite his return to Populus, he will continue to provide advice to the Prime Minister – “becoming a key part of the general election campaign team at Conservative Campaign Headquarters, where he will be responsible for overseeing the sophisticated data analytics that will be at the heart of the campaign”, according to a statement.

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.”

Populus CEO Michael Simmonds added: “Andrew’s considerable experience brings an added ingredient to the business. We are very pleased to welcome him back and to be able to add someone of his talent and experience to our team.”