Toyota will begin a year-long pilot of 20 plug-in hybrid Prius models from May.
The Government will run 16 with the remaining four going into fleets already running a large number of Prius cars.
Toyota will use the trial to gather data on how the cars are used and how often they are used, including mileage covered and charging frequency.
The data from the UK trial and others in mainland Europe will enable the company to create a balance between size of battery and the average range requirement.
A smaller battery allows greater boot space but reduces the range.
A production version of the Prius plug-in hybrid, which uses a lithium-ion battery and emits 59g/km CO2, will go on sale in the UK in 2012.
It is chargeable using a standard electrical plug, says Toyota, and takes 90 minutes to charge.
Plug-in hybrid is one of four alternative fuels Toyota believes will form the future of car propulsion; the others are electric, fuel cell and its existing hybrid technology. All sit on one platform – the Hybrid Synergy Drive.
Electric is expected to come to market in 2012, with fuel cell expected in 2015. Fuel cell technology uses a hydrogen tank to produce electricity on board. Toyota says it offers a range of 800km.
It is already running a test fleet of 100 fuel cell vehicles worldwide and is talking to fuel suppliers about investing in the technology and infrastructure.