48-year-old Coulson, who was the former editor of the now-defunct Rupert Murdoch owned tabloid 'News of the World', has set up Coulson Chapell alongside Pitch PR firm founder Henry Chappell.
According to the UK Companies House records, the firm was set up earlier this month and offers clients"discreet corporate strategy and communications advice".
"From our combined experience, Coulson Chappell can offer a unique perspective to clients looking for clear, discreet and effective strategic advice," Coulson was quoted as saying by the Guardian newspaper.
Following the 2010 general election, he was appointed as communications chief at Downing Street by Cameron, then newly-appointed prime minister.
About a year later, he was arrested over phone-hacking allegations following his resignation from Downing Street in January 2011.
He was charged with conspiracy to illegally intercept communications and in June 2014 was found guilty of the charge and sentenced to 18 months in prison.