Supermarket shoppers will have to pay 5p for single-use carrier bags from next week under a new law introduced to stem litter and help wildlife.

Here’s what you need to know about the changes.

What's happening?

The government has introduced a law requiring all supermarkets and large stores to charge a minimum of 5p for every single-use plastic carrier bag they hand out in a bid to reduce their use and the litter they cause.

When is the charge being brought in?

The charge comes into effect in England on October 5.

Does it affect all retailers?

No. The charge applies to retailers with 250 or more full-time equivalent employees, determined by the size of the company rather than the individual branch.

Smaller businesses can charge if they wish, and the Association of Convenience Stores says it is encouraging members to introduce their own voluntary charging schemes wherever practical.

Are there any exemptions to the charge?

Yes. There will not be a charge for paper bags or bags from shops in airports or on trains, aircraft or ships.

Customers will not need to pay if the bag only contains certain items such as unwrapped food, raw meat and fish where there is a food safety risk, prescription medicines, uncovered blades, seeds, bulbs and flowers or live fish.

What about supermarket home deliveries?

Retailers must charge for plastic bags used for deliveries and online sales. Choose the bagless delivery option if one is available to avoid the charge.

Tesco has alerted its customers that unless you choose bagless delivery there will be a 40p flat charge for home shopping. Sainsbury's has also introduced a bagless delivery service, and those who do not select it will also be charged 40p per delivery.

What can consumers do if they do not want to pay the charge?

Shoppers can avoid the charge by using their own bags or containers. Typically, stores charge once for a ‘bag for life’ and replace them for free when they wear out.

Why is it being brought in?

The number of single-use carrier bags handed out by supermarkets in England rose for the fifth year in a row in 2014 to 7.6 billion, the equivalent of 140 bags per person. Campaigners warn they take 1,000 years to break down, are a highly visible type of litter, use resources and can be extremely damaging to marine wildlife.

Will it work?

Similar schemes in other parts of the UK have had a significant impact. The scheme in Wales - the first to come in - saw a 79 per cent reduction in plastic bags being handed out in the first three years, while Northern Ireland and Scotland have also seen reductions since they brought in charges.

The government expects to see a reduction of up to 80 per cent in the use of single-use carrier bags in supermarkets, and 50 per cent on the high street in England, as well as £60 million saved in litter clean-up costs and £730 million generated for good causes.

But there are concerns that the exclusion of smaller retailers and paper bags means it will not be as successful as other schemes.