The two organisations will promote each other's services, with Bethell also agreeing to pay Motorvate membership fees for any local authority that signs up as a customer.
Through the Motorvate scheme, fleets sign up to a 12% reduction in CO2 emissions and a 3% reduction in business mileage over a three-year period.
Bethell customer Vale Royal Council, has become the first to sign up to the scheme under the joint programme, becoming Motorvate's ninth local authority client.
Motorvate scheme manager Rob Anderson said: 'We are excited about the potential for this partnership. At the moment, it is confined to local authorities, but it is ripe for expansion.'