When it comes to packaging, there is a clear hierarchy in public perceptions. Plastic is the root of all evil. Aluminium is more of a minor offender. Recycled materials earn a few brownie points. And paper is probably the best we can do, if we can’t avoid packaging altogether.

So the latest commitments from Morrisons and Waitrose are likely to go down well. Both are ditching plastic bags for life trial basis, with the view to a wider rollout if things go well. While Morrisons is replacing its plastic bags with paper versions, Waitrose is yet to confirm what alternatives there will be, if any.

Either way, it certainly sounds like a change for the better. Morrisons says the move could cut plastic bag use by 90 million bags a year, which equates 3,510 tonnes of plastic. Waitrose says it will remove 40 million bags a year from circulation if the scheme goes to plan.

As both retailers know, there are genuine reasons for those negative public perceptions of plastic. No one wants notoriously slow-degrading plastic bags clogging up landfill sites – many of those supplied by supermarkets do, according to Morrisons – or adding to the problem of plastic pollution in our oceans.

But switching to paper isn’t quite as straightforward as it may first seem. A research paper by the Northern Ireland Assembly in 2011, which measured the environmental impact of different options, found it “takes more than four times as much energy to manufacture a paper bag as it does to manufacture a plastic bag”. And let’s not forget what paper bags are made from. You need to cut down forests to produce the paper in the first place.

What’s more, the study found paper bags needed to be reused at least three times to make them more environmentally friendly than a single-use plastic bag. That’s only slightly less than the plastic bags for life, which need to be used four times.

And there is a question mark over whether this will happen. Although Morrisons says many reusable plastic bags go straight to landfill, it is nevertheless common to see customers bringing in their ‘bags for life’ – and the term very clearly communicates that it is meant to be used more than once. Whether they will do the same with paper options, which are generally perceived as more disposable and biodegradable, remains to be seen.

Morrisons has put plenty of effort into addressing these issues. In terms of the manufacturing process, it has ensured the bags are sourced from forests that are managed responsibly, and are manufactured at an eco-powered site in Wales. It also points to the strength of the bags – they have a similar capacity to a standard plastic bag for life and are strong enough to carry heavy weights up to 16kg, according to Morrisons. That should make them more likely to be used again, rather than ripped and thrown away.

Those efforts must be applauded. But the ultimate test will be public behaviour, and whether they see paper bags as truly reusable. Because as the packaging debate shows, perceptions are everything.