The money-generating measure was outlined at Stormont on Wednesday by the Finance Minister as part of the long-awaited draft budget.

Sammy Wilson said that by charging shoppers 15p per bag, the government could generate £16m over the next four years towards balancing the £4bn spending cuts.

However, Ulster University retail analyst Donald McFetridge has slammed the tax as "ridiculous", saying it could add up to £468 a year for households and £93.60 for individual shoppers.

"When I first did the sums, I thought I'd got it wrong and even reached for my calculator to verify that I hadn't got the decimal point in the wrong place," Mr McFetridge said.

"The plastic bag tax announced in Minister Wilson's NI budget is absolutely ridiculous.

"Taking 20 bags, at 15p each, costs £3 per visit. For three visits a week that's £9, and for 52 weeks a year almost £500 for plastic bags for the average household."

Mr McFetridge says his figures are based on household which typically spend around £100 a week at supermarkets.

They don't take into account double bagging for heavy items such as washing powder and bottles, or the need to keep items with could taste or scent other products separate, he continues.

But Sinn Féin MLA Daithí McKay said there are significant environmental advantages to the bag tax on top of the money it would generate.

"This levy will not only raise revenue for a programme which will improve energy efficiency, create jobs and assist those in poverty but it will also greatly reduce the problem of plastic bag litter in our communities," the North Antrim representative said.

"The fact that these proposals have been adopted by the Executive is very much an endorsement of the work Sinn Féin has done on this issue over the past three years."

Meanwhile on the streets of Belfast, shoppers have had mixed reactions to the plan.

"If it's going to bring money in then yes - there's no way of disposing of a plastic bag," one man told UTV.

Another said: "I think it's a good idea. We need to do everything we can for conservation and it'll make people think twice about just lifting bags."

But another woman told UTV: "No, 15p is a wee bit too much."

Comments:

At 12:42 on 16 December 2010, Willie.g wrote:
This article is just a joke. I moved to the republic 2 years ago. I bought some reusable bags and have maybe paid the levy half a dozen times as I went to a shop on the spare of the moment, otherwise I have my bags with me and therefore avoid the plastic bag levy.

At 12:11 on 16 December 2010, Paul wrote:
Its not exactly rocket science. People in the Republic have been doing it for a good few years now. You buy a few sturdy bags and put them in your pocket, car, bag and take them with you when you go shopping. The bags are reusable so you only have to buy them once. Why then are people harping on about how this is going to cost them £100's of pounds a year? As usual, people have to blow things out of proportion so they can enjoy a good whinge. The nice thing about this is the effect it will have on the environment. Its about time it was done.

At 09:28 on 16 December 2010, Chris wrote:
Not once did Donald accept, or refer to the impact on the environment that the over use of plastic bags cause. Anyone can see that the charges for the bags are not to raise money, but to make people think twice about the amount of bags they use, or god forbid, use a green reuseable bag.

At 08:56 on 16 December 2010, Benny wrote:
I would advise Mr. McFetridge to go and do his figures again. Anyone that needs 60 bags to carry £100 of shoppng has a serious issue.