Murphy has left his post as head of APCO's global services to government division to establish the new outfit, named Centreground Political Communications.
The public affairs heavyweight joined APCO in 2005 after three years at Number 10, first as assistant political secretary to prime minister Tony Blair, and then as Blair's special adviser on political comms.
It is expected that the new operation will not be a straight public affairs outfit but will instead specialise in offering campaigning advice to governments, corporates and NGOs wishing to occupy the political centre ground.
It is understood Murphy, a loyal Blairite, plans to link up with a number of former colleagues who share his political outlook. A well-placed source said Murphy had spoken to a number of Blairites with campaigning experience about his new venture.
Murphy confirmed he had left APCO to establish the consultancy but said he was not yet in a position to speak further.
He was promoted to become global head of APCO Worldwide's services to government practices in 2009, having previously been UK MD.
Murphy entered the government machine in 1997 as a special adviser to then deputy prime minister John Prescott, going on to serve as an adviser to Alan Milburn during his four years as health secretary.