Citroen C1 HDi Rhythm

The 1.0-litre petrol-powered version manages 61.4mpg in the combined cycle, but if you want more, there's a new diesel variant in the range. With fuel consumption of 68.9mpg, it's one of the most economical cars on the planet.

The C1 is all about minimalism. Weight is low, the dimensions are small and as a result the price can be kept down, too. However, soundproofing is something that the Citroen could do with a little more of. While refinement is not a problem with the three-cylinder petrol model, the rattly diesel is far more intrusive.

What's more, the 55bhp unit lacks power, and is noisy when full throttle is applied, proving particularly grating on motorways. Citroen quotes a 0-62mph time of 15.6 seconds, and the C1 has to be pushed hard to keep up with traffic. Thankfully, its five-speed manual gearbox has a positive throw.

Aside from its lacklustre engine, the newcomer is as characterful and capable as its petrol counterpart. The tidy handling and direct steering are perfect for nipping in and out of traffic in the city, and the tiny runabout fits into the smallest spaces. Combine this with a light and spacious interior, and it's clear that it's the engine which lets the package down as a whole.

While the running costs will fit into any motorist's budget, the ΂£1,100 price premium over the petrol model seems excessive. It's also questionable when compared to Fiat's capable Panda 1.3-Multijet, which is ΂£7,895, while full-sized superminis are also within reach.

Vauxhall's Corsa CDTI might not be the freshest in its class, but it beats the C1 hands-down for refinement and costs only ΂£100 more in basic diesel form. The Citroen is a fine city car, but makes far more sense with a petrol engine.