it's a bit of a chicken and egg situation (although that assumes the government want to reduce congestion and the amount of traffic on the road and not simply rake in cash!)
We have a poor public transport infrastructure - especially if you live outwith a city.
to get people out of their cars they need to put the infrastructure in place to give viable alternatives. How do they pay for that? well, money from the public transport itself, but also road tax revenues should be used, and i think the transport companies who are making the profits should be taxed to pay for it too.
and yeah, the people who drive and park in congested towns/cities should have to pay too.
I don't think passing it onto businesses is the right way to do it, rather the "driver" should be the one who pays
but the upshot of it all will be that people will simply desert town centres where it's either congested or expensive or impractical to get into with a car (due to lack of affordable parking)
this means cars will flood to out of town shopping - where there is FREE and plentiful parking!! So, maybe free parking shouldn't be an option for any retail park/supermarket and all the revenue from it is put towards paying for public transport services to/from the sites to alleviate some of the traffic
either way - it won't be free. we'll pay for it all somehow
that's why i shop online, it's a lot less hassle!!