The 5p charge for single-use supermarket bags in England from next month will cost taxpayers £1.5 billion over the next decade, a pressure group has claimed.
The Taxpayers' Alliance said the "shopping tax" will add £67 to the cost of living per household in England over 10 years.
From October 5, large shops in England will be required to charge 5p for all single-use plastic carrier bags.
All retailers with 250 or more full-time equivalent employees will have to charge a minimum of 5p for the bags they provide for shopping in stores and for deliveries.
The alliance said its £1.5 billion figure comprised £1.1 billion for the 5p charge, £348 million for substitute bags for life and bin liners, £70 million of additional VAT and £5 million of taxpayer enforcement.
The legislation was poorly targeted and the term "single-use" failed to reflect that the bags were often re-used.
It concluded that the charge "is unlikely to fulfil its stated aim of reducing waste and resource use, while piling on additional costs that will be borne by consumers".
TaxPayers' Alliance chief executive Jonathan Isaby said: "This plastic bag charge is to all intents and purposes a shopping tax which will add more to the cost of living for families throughout England.
"Politicians rightly identify the cost of living as a huge concern to people, yet seem oblivious to the irony that their own actions are adding to the burden.
"This is yet another example of a well-intentioned yet badly-thought out proposal which is being introduced without considering the full cost implications for consumers.
"Taken together with the minimal benefits for the environment and the potential for the charge to increase over time, this appears to be a very ill-considered policy which will fail to achieve its stated aims."
The number of single-use plastic bags handed out by UK supermarkets increased for the fifth year running to 8.5 billion, the most recent figures from the Department for Environment, Food and Rural Affairs show.
The number is up by 200 million on 2013 despite the average household already having 40 plastic bags stashed away.
In England, the number of single-use bags from supermarkets rose from 7.4 billion in 2013 to just over 7.6 billion, the statistics from waste reduction body Wrap revealed in July.
Northern Ireland saw the number of bags handed out plummet once again by 42.6% following a previous drop of 71% after a carrier bag charge was introduced in April 2013.
In Scotland, which brought in a levy last year, there was an 18.3% decrease in the number of plastic bags handed out by retailers.