The warning comes a day after Marks & Spencer said it would start charging food shoppers five pence per bag, with the money going to improve parks and play areas.

'I am convinced we need to act - and the time to act is now,' Mr Brown wrote in the Daily Mail newspaper. 'And I want to make clear that if government compulsion is needed to make the change, we will take the necessary steps.'

'We do not take such steps lightly - but the damage that single-use plastic bags inflict on the environment is such that strong action must be taken,' he added.

Last year Mr Brown struck a deal with the supermarkets to cut the environmental impact of plastic bag use by 25 per cent through reducing their numbers and increasing the content of recycled plastic.

But he said more needed to be done, which was why he wanted the bags to carry a price to deter usage.

'I have already made clear that over time we should aim to eliminate the single-use plastic bag altogether,' he wrote.

'Other governments are seeing how they can curb bag use - Ireland, Australia, Denmark and parts of America and India have been trying different ways to cut the unnecessary waste. We are looking at all this international evidence to see what steps we in Britain should take next.'

While Ireland and Denmark had introduced a tax on plastic bags, Australia had adopted a more voluntary approach and even there usage had dropped by half.

In South Africa where plastic bags have become a major environmental menace, shoppers now have to pay for them. -- REUTERS