Reducing demand for plastic carrier bags? Some pros and cons!

The weekend announcement by one political party that they want a mandatory charge on disposable plastic carrier bags, subject to public approval raises a number of questions.
At 5p a bag and with the profits going to charity the majority of consumers will think of it as a charity donation and feel good every time they buy one, two, three or even a dozen.
If the money is paid into the exchequer it may be expensive to collect, administer and police.
The price may then have to go up to £1 a bag.
The increased use of fabric re-usable bags may result in increased cross contamination.
When did you last put yours through the washing machine?
Did that chicken leak into your bag?
Would you buy some loose salad salad produce and bother to buy a plastic bag?
Another unexplained random outbreak of Campylobacter gets under way all for the sake of 5p!