Keenan will remain a consultant to the company for a minimum of six months, and subject to quarterly reviews beyond that.
Keenan is understood to be working on the launch of a bridging lender.
The news follows the collapse of management buy-out talks earlier this year, which could have seen the network de-listed from AIM.
Keenan says: “As co-founder and one of Prestbury’s largest shareholders, I will continue on a personal and professional level to be passionately committed to the Prestbury business and will continue to work with chief executive Lee Birkett and the Prestbury team as required.
“Prestbury is a great business with great people and I confirm my support for the executive directors. I can also confirm I will be retaining my shareholdings in Prestbury Holdings.”