You'll know about Ikea. It's the place you drive to on a Saturday to fill your house with bits of wood from foreign lands.

This week, they played a little April Fool's joke, with some viral marketing about launching a new "Leko flatpack car".

When unveiled it turned out to be a computerised car-sharing scheme in France. Not a new one, but a special customised service from an established car-sharing service designed to get more customers to Ikea stores.

Now, I am in favour of car-sharing. Anything to keep down the number of cars clogging up Ikea car parks must be good. But this story is a bit like the one I did on Disney theme parks a couple of weeks ago. It is green tinsel on a business model that is all about persuading people to make long carbon-intense journeys to buy their products.

The telling statistic was at the back end of the company press release: "5.8% of Ikea France's customers already used a shared form of transport to get to their preferred store." So 94.2% don't. Allowing for the odd walker and cyclist, that must mean around 90% drive.

That's the problem, Ikea. You build your stores in places out of town that are ill-served by public transport. You slap a big delivery charge on any who don't want to take their own furniture home (£60 in my case, I notice). And then you try and get greenie points for making it slightly less hard to reach them in an environmentally acceptable manner.

It won't wash.

The car-sharing scheme is part of a rather haphazard greenwash strategy that has been going on at Ikea for a while. Last week its website announced that "Ikea has signed up to WWF's Earth Hour 2009."

Earth Hour is an annual event promoted by the environment group WWF in which we are all encouraged to turn off our lights for an hour as an expression of support for cutting greenhouse gas emissions and halting climate change. This year that hour was from 8.30pm on 28 March.

Ikea didn't turn all its store lights out. It might have been bad for business. Instead it "turned all lighting in-store to minimum levels consistent while maintaining a safe working environment for co-workers and customers." Shouldn't they do that all the time? Or, since only half of their UK stores stay open that late on a Saturday, they could have shut the rest, allowing all the lights to go out. Just a thought.

In any event, I am not quite sure why WWF allowed lights-on Ikea to use its logo to promote how it had "signed up to" (but not obeyed, obviously) the Earth Hour. Nor why it gave Ikea gratuitous publicity on its own site for half-heartedly complying with the Earth Hour.

Well, actually I am fairly sure. Ikea and WWF have a long-term "business relationship". Ikea gives cash and a few environmental initiatives, while WWF gives green kudos and some environmental advice.

The panda logo is all over the Ikea website. Ikea is all over WWF's website.

There have been some hard questions asked about this relationship among other green groups. The Environmental Investigation Agency, for instance, recently pointed out that Ikea has not even managed to stamp out the use of illegally logged timber in its furniture, especially all those flat-packs supplied from China.

Worse, the company has been actively opposing US laws set to come into force in July aimed at banning imports of illegally logged timber. Unless the company gets it overturned, every piece of furniture sold in an Ikea store in the US will be required to have a paper trail showing where the wood came from.

Even though other companies claim to be able to meet the rules, Ikea told federal regulators that "trying to trace this information to certify compliance all the way through the supply chain to the harvesting of each and every tree is unrealistic."

For unrealistic, read expensive. Perhaps WWF should give back that sponsorship money and ask Ikea to spend it checking its supply chains. Or is that "unrealistic" too?

Who are the real greenwashers this week? Well, I think WWF should share the accolade with Ikea, for services rendered.

• Do you know of any green claims that deserve closer examination? Email your examples of to greenwash@theguardian.com or add your comments below