The deal, which will see Manheim dispose of 50,000 cars, vans and motorbikes until at least 2006, will include 16 branded sales held each month at nine of Manheim's 18 auctions sites across the UK.
About 40% of First National vehicles are refurbished by Manheim using 'smart' repairs and most are given a 40-point check and five-day money-back guarantee.
Martin Potter, corporate sales director at Manheim Auctions, said: 'Some buyers will only buy First National vehicles as they have confidence in the quality of the vehicles on offer, which means First National branded sales are consistently high.
'Offering a quality product has also seen First National unaffected by market falls in residual values, with buyers prepared to pay more than the market values simply because they know First National does everything possible to offer them a quality vehicle.'
Manheim claims to be achieving an average of 101% of Cap clean prices on all First National vehicles sold, along with a 96% conversion rate.
Howard Watkin, director of arrears management for First National, said: 'The improved quality of the vehicle presentation at auction has increased buyer confidence and loyalty to the First National brand, which has translated into improved results.'