Footman James has been put up on the market for a reported £60m.
The specialist car broker will be sold by its private equity owner Alchemy Partners with several prospective buyers already lined up to acquire the company.
Potential buyers are understood to include the AA, as well as several private equity investors.
The sale of Footman James is the latest investment to be put on the market by the private equity company.
Earlier this month, Alchemy confirmed that it was seeking advice on a "possible exit" from broker Open and Direct.
Accountancy firm Deloitte is understood to have been appointed to sell both businesses.
Footman James was founded in 1983 and specialises in classic car and motorbike insurance, as well as insuring kit and replica cars.
It also offers both household and commercial insurance to its 140,000 policyholders.
