As the SmartPlanet team will tell you, becoming a parent often miraculously turns individuals from carbon criminals into green paragons overnight. Many new parents suddenly get interested in organic food and clothing when Baby arrives, so picking a family car with a low-carbon twist is a natural progression.

Below, we've rounded up seven options to consider. They fall into three categories that go in size order. First are the small family cars, which include the Prius, Honda's hybrid and Ford's ECOnetic Focus. Second are the large family wagons, which include the Renault Laguna and VW BlueMotion Passat. Lastly, there are the 4x4 family cars: the Lexus RX400h and Subaru Legacy Outback.

If you're keen to pay only the minimum vehicle excise duty (VED) under new government plans, you can scratch the Lexus, VW and Subaru off your list. All three exceed the carbon emissions required to get into the proposed new sub-£90 band. Direct.gov has full details about the new VED (erroneously referred to as 'road tax') plans.

Understandably, you'll want space in your family car. If boot space and interior space are your priority, the Renault Laguna and VW BlueMotion Passat are the best bets here. All these cars, however, offer a minimum of adequate storage space for carrying folded buggies and other child paraphernalia.

Safety will also be paramount in your mind. European safety testing body Euro NCAP rates the Prius highest on child safety and the Honda and Passat lowest. It's worth bearing in mind, however, that all the cars tested still scored highly for child safety. Here's the breakdown for the 'child occupant safety' scores:

-- 2004 Toyota Prius: 43
-- 2005 Renault Laguna: 41
-- 2004 Ford Focus: 40
-- 2007 Honda Civic Hybrid: 38
-- 2005 VW Passat: 38
-- Lexus: no data
-- Subaru: no data

But let's cut to the chase: which is the greenest of this bunch? It's a very close three-horse race between the Focus, the Prius and the Civic Hybrid. On local air pollution and CO2 emissions per kilometre, the Prius wins. The Focus, however, is still worth a look as it's significantly cheaper than the Prius.

So which green family car is for you? Read our full reviews below to learn more about the driving experiences and just how green each car really is.