THERE were good reasons for introducing the 5p charge for plastic bags in Scotland last year. Not only are discarded carriers a threat to wildlife, they often end up in landfill and can take hundreds of years to break down. It also costs millions every year to deal with plastic waste. Charging 5p a bag was the least we could do to tackle a serious environmental problem.

One year on, we can also say with confidence that the policy has started to work. Within weeks of the charge being introduced in the final 11 weeks of 2014, there was an 18 per cent drop in the use of plastic bags and the trend has continued in 2015. According to the latest figures, 650 million fewer bags have been handed out since October 20, 2014 - the equivalent of 4,000 tonnes of plastic waste. What’s more, over a year, the 5p charged has raised nearly £7million for charity.

The reason the policy, which the Environment Secretary Richard Lochhead has rightly hailed as a major success, has worked so well is that it is simple to grasp and represents a subtle nudge, rather than an aggressive push, to encourage consumers to change their behaviour. England has also followed suit, although it has lessons to learn about keeping the policy simple. Instead of introducing a relatively simple charge with few exemptions as Scotland, Wales and Northern Ireland have done, the Government in England has allowed a confusing series of exemptions; stores which employ fewer than 250 full-time employees are also exempted from applying the charge. The lesson of the policy elsewhere in the UK is that it is better to keep it simple.

However, the Scottish Government should be wary of becoming too smug on the issue. The £7million raised for charity by the 5p charge represents millions of people who are still using single-use plastic bags and need to be convinced, or encouraged, to change their ways. Re-usable plastic bags also have an environmental cost, so no one should assume the problem of plastic waste is solved – indeed, anyone driving around Scotland can see the litter and know that not to be the case.

Richard Lochhead was right when he said the 5p policy was a success, but it may be that the policy, sooner rather than later, will need toughening further. Scotland’s problem with litter and waste is far from solved.