The charity, which has approached agencies directly, hopes to modernise its image and raise its profile in the UK ahead of the 2012 Olympics in London. It will appoint an agency on a five-year contract.
The search is underway and a decision is expected next month. It is not known whether the incumbent, Feel, will repitch.
Last year, the charity overhauled its branding for the first time in 39 years ahead of the Olympics. It retained the distinctive white cross, but dropped the strapline: "Caring for life."
The new identity will be rolled out across signage, literature, uniforms and online over the next five years.
The rebrand coincided with an advertising campaign in April last year to encourage people to learn first aid. Created by Feel, the campaign featured childlike ragdolls. It asked the question: "Would you know what to do if this was a real child?"