Former FPR chairman and director Simon Preston told PRWeek that MacLeod had decided to step down at the age of 62 due to ill health.
Preston added that FPR and its offices in London's International Press Centre had been put up for sale as a debt-free shell company.
The company hopes to drum up interest in FPR's brand and the possibility of a buyer using its revenue losses as a write-off against taxes on profit.
Preston said the company had not handled any PR clients over the past year and had instead been engaged in 'a technology venture'.
He declined to give any further details.
FPR was originally set up in 1968 by Lord Alport. The company ceased trading as a financial PR and IR consultancy in the early 1980s before MacLeod revived it under the same trading name in 1989.
At its height, FPR had clients including General Accident, which later merged with Commercial Union and Norwich Union to form CGU.