Supermarket shoppers could soon have to pay more for their single-use plastic bags following reports that the 5p charge is set to double and be extended to all shops.

Here are some key questions answered on the carrier bag levy.

When was the plastic bag charge introduced?

The plastic bag fee came into effect in England on October 5 2015.

The Government introduced a law requiring all supermarkets and large stores to charge a minimum of 5p for every single-use plastic carrier bag they handed out.

Under the new measures, the charge would reportedly double to 10p.

Why was it brought in?

The carrier bag levy was introduced in a bid to reduce their use and the litter they cause.

In 2014, the number of single-use carrier bags handed out by supermarkets in England rose for the fifth year in a row 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.

Which shops are currently covered by the charge?

Currently, 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 have been allowed to charge if they wish, while the Association of Convenience Stores has encouraged members to introduce their own voluntary charging schemes wherever practical.

According to reports, Theresa May is expected to lift the exemption on small businesses, and extend the charge to all stores rather than just large retailers.

What impact has the fee had?

Disposable carrier bags issued by the seven biggest supermarket chains have declined by 86% since the charge was introduced, official figures show.

The total number of single-use plastic bags sold by all 249 retailers who reported in 2017-18 was 1.75 billion – down from 7.6 billion in 2014.

What happens to the money raised by the scheme?

The plastic bag charge is not a tax, and does not go to the Government.

Retailers are given the choice what to do with the proceeds, but they are expected to give it to good causes.

Between April 2016 and 2017, almost two-thirds of retailers reported giving more than £66 million to good causes – amounting to four pence for every single-use bag sold by them.