COI bosses hope to add two or three more regional shops to the five on the Government's roster to reflect an increasing number of regionally based campaigns and greater use of pilots before ads are rolled out nationally.
Peter Buchanan, COI's deputy chief executive, said the performance of regional agencies was improving as they attracted more people in the industry who wanted to move out of London.
"The quality is better now," he said. "We would like to see a few more regional agencies on the COI roster."
COI officials have begun sifting through applications by 123 agencies trying to win a place on the roster, which includes 25 shops and three specialist recruitment agencies. The list is expected to remain broadly the same size.
The review is likely to lead to agencies that have established themselves since the last shake-up four years ago joining the roster. Those expected to apply include Clemmow Hornby Inge, Vallance Carruthers Coleman Priest and Campbell Doyle Dye.
All the shops on the new list will probably have the opportunity to pitch for at least one government campaign over the next four years.