Crighton, who is understood to have left Edelman because travel commitments kept him from his family, has joined Banner PR as senior PR consultant working on a part-time basis.
In his new role, he will work closely with the tech agency's recently appointed director of PR Tracey Pretorius on business development.
Pretorius said Crighton was hired as part of her plans to beef up management of the firm's PR division, but that no further management appointments were in the pipeline.
He will work as a consultant from his Ireland home, said Pretorius, 'commuting to London on a needs-be basis'.
'Since I started in February, my goal has been to grow the PR division.
I wanted somebody on board to consolidate our offering,' said Pretorius of Crighton's appointment.
Banner Corporation offers a range of marketing services including PR, interactive and advertising.
'The company's largest PR client is Cisco Systems,' said Pretorius. The PR division works for the firm in 33 countries across the EMEA region.
'We're London-based, but do European outreach only,' Pretorius added.
Although Crighton's brief will mainly consist of 'design and implementation of good client programmes', according to Pretorius, he will also provide senior counsel to clients.
Meanwhile, it has emerged this week that Stephen Doherty has quit as a director of Edelman's UK corporate and public affairs business. Edelman UK CEO James Thellusson said that Doherty will not be replaced. Doherty leaves just five months after being promoted from associate director to director.