Ford is planning a high-economy, low-CO2 Econetic version of the new Ka - but hasn't yet decided whether it will be petrol- or diesel-powered.
The new Ka is based on the Fiat 500 and uses Fiat engines, which means it is available with a small diesel for the first time a 74bhp 1.3-litre unit.
With standard exconomy of more than 67mpg and CO2 emissions of just 112g/km, this would be ideal for turning into an Econetic.
Buyers could expect well over 70mpg and sub-100g/km emissions, making the car exempt from road tax.
However, it would almost certainly be an expensive economy car, and Fiat is working on a new range of small petrol engines which might be better-suited.
These will be turbocharged units of around 900cc and have air-operated valves, dispensing with conventional camshafts, so they would be light and small.
Ford might well decide that one of these is a better bet for the Ka Econetic.
The company is equally non-committal about the prospects for a new Sportka and convertible Streetka.
The Fiat 500 range would give Ford access to engines and platforms for both, but Ford says it has not yet decided whether to proceed with either.