I refer to the above report which was published last week. I agree with your findings - specifically that less than 1% of plastic bags become litter, and that the Government's commitment to end plastic bag use should not proceed unless it is supported by a transparent cost-benefit analysis. Unfortunately, as is often the case with government's, the process will not be transparent, and it will be a case of appearances being used for political expediency - being seen to be doing something, even if that something actually doesn't make that much difference. As you state, 75% of households reuse plastic bags rather than throw them out - we certainly do in our household. If supermarkets cut them out, we will just have to buy plastic bags - for our food safety requirements, and for storing litter. So it will just be a boon for plastic bag manufacturers, and given people will not be able to reuse plastic bags from supermarkets, one can see a situation where actually more plastic bags are manufactured and used, as a result of an increase in demand.

Cheers,
Martin