Has the National Trust got the nerve?

Army of millions ... could the National Trust transform itself into the world's biggest environmental organisation? Photograph: David Levene

I like the idea of the National Trust becoming less of the purveyor of fine property and more of an environment movement. I applaud its intention to help its 3.5 million members address climate change, and I really do want it to link the disparate conservation and environment movements. Of all the myriad groups who are concerned about the state of the local, national and global environment, it alone has the muscle, credibility and sheer bulk to challenge government and scare the life out of ministers and local authorities.

If you speak for 3.5 million members you carry a lot of political weight into a meeting. But has it got the nerve? The trust to me has always been a big green neutron bomb, a weapon of deterrence that only needs to be shaken at opponents to achieve results. But I fear the bomb-making equipment has gone rusty and high command may be a long way from the trenches.

Ok, it challenges a public a road here, or a development here. It lets it be known that it lobbies quietly in the corridors of power for broad changes. It murmurs into ministers' ears at establishment events.

But whose interests has it really served beyond its own? It is so powerful that there are few developers who will dare propose anything that might offend it, and few local authorities who will say no to anything it wants. It looks after itself very well.

Such is power and influence, but that's very different from leading the environment debate. That is not safe. It requires it to challenge power, lose friends and members if necessary, to forego privilage and accept riducule.

Take airport expansions - the trust rightly wants to stop Stansted expanding and rendering its nearby Hatfield forest unvisitable. But will it help the people of Wolverhampton, or Gatwick or Bristol challenge their airport expansions? Is it happy to be monstered by the Mail or the Sunday Times? Or No 10. Is it frightened about its own charitable status? Can it take the flak?

And what about roads? Or air quality or pylons, or green belt? Where does it stand on these? The trust memorably opposed some bits of the £24m road programme in the 1990s but hasn't said much at all about the new programme which is only going to encourage more cars. And where was the trust when it came to the marine bill?

It has grown finanacially fat by playing safe and allowing other groups to fight its battles. Now it's payback time. It needs to be very brave and recognise it is not an island of ecological loveliness set in a degraded sea that others must clean up. It must work to change what is around it, if only to to protect itself. It will find it has many new friends.

The trust is the last great mutual organisation in Britain, and its purpose was never to be moderate but to "be of benefit to the nation". By its charter it is there "for ever and for everyone" and "to promote the preservation of places," and if that is not to openly promote genuinely sustainable development then what is?

In other words, it has a duty to speak out. As it knows from its own history, nothing ever gets done in Britain except by people standing up and making a fuss. But does it have the bottle?