According to newspaper reports, the Financial Service Authority (FSA) is to implement the ban following a year-long investigation.
The probe focussed on the work of the global markets and banking division at RBS, a unit headed by Mr Cameron.
He led the financial institutionâs work on the takeover of Dutch bank ABN Amro, a move many believe helped exacerbate the bankâs financial difficulties and led to government bail outs during the credit crisis.
Although not accused of any illegal behaviour, the banker has agreed to the FSAâs ruling and is not expected to launch an appeal against the decision.
Mr Cameron will be able to take on short-term consultancy posts, pending on approval from the FSA.
The FSA investigation examined âconduct, systems and controlsâ at the division of RBS.
Last month, the regulator issued fines and bans to two former directors of failed bank Northern Rock.
David Baker, former deputy chief executive at the financial institution and Richard Barclay, ex-managing credit director, were given fines of Â£504,000 and Â£140,000 respectively.
By Jim Ottewill