The new wildlife website which my wife and I have just launched (and seems very rude to link to as a new member here) is currently backing the Daily Mail campaign to ban the carrier bag. Whilst their coverage of it is very one sided - we have tried to present both sides; in a nutshell many people object to it on the grounds that there is that much other plastic produced that carrier bags are not that big a part of the problem; our take on it was and still is that anything we can do to help we should. Whilst it may be a part of a much bigger problem it is still well worth starting here.
The direct link to the daily mail campaign and petition is:
Sign the Daily Mail's online petition to banish plastic bags | the Daily Mail