Between 2006 and 2009 carrier bag use was down by 40% but in 2010 the downward trend was reversed

British consumers are packing away their green credentials along with their weekly shop, as last year an increasing number of us bundled our purchases into single-use plastic carrier bags instead of seeking out environmentally friendly alternatives.

Plastic bag use plunged after 2006, when the government, retailers and green campaigners spearheaded a push to cut down on the 11bn plastic carriers Britons used each year, most of which find their way into landfill or – much more damagingly – into waterways and the sea, where they are a hazard to marine life.

By 2009, bag use was down by about 40% to under 6.5bn.

But last year, that downward trend was reversed. Perhaps owing to recessionary worries, people forgot their hessian sacks and filled up on plastic again - more than 6.8bn were used, up about 5% on the previous year, according to the government's Waste and Resources Action Programme (Wrap).

Recycling minister Lord Henley said: "This isn't good enough. Retailers need to take responsibility and lift their game to cut down on the number of single use carrier bags they hand out. If results do not improve we will consider additional measures to make this happen, including legislation."

The British Retail Consortium said part of the increase was likely to be down to shoppers making more short trips to stores, rather than a single big weekly shop. But the retail trade body said the small increase should be put in context of the "massive" progress made since 2006, and said plastic bags were only one of the many ways in which retailers were cutting their environmental impact.

Bob Gordon, head of environment at the British Retail Consortium, said: "It's encouraging to see the majority of consumers are continuing to reuse their carrier bags and are taking as few new bags as possible. We urge customers to keep that up, particularly when changing shopping habits, including more trips to stores, present a challenge to maintaining the progress made in recent years."

He rejected calls for a bag ban or charges, which could penalise shoppers at a time of financial hardship. "The overall numbers remain the sort of result other environmental campaigns can only dream of," he said. "But it's time to accept bags are not the be-all and end-all of environmental issues."

Plastic bag data is difficult to compare over the past five years, because of changes in the way the statistics are collected. Between 2008 and 2009, the data was collated on a mid-year basis, from June to May, but from last year Wrap decided to return to presenting it on a calendar year basis.

In 2006, nearly 11bn single use carriers were used, but after campaigning this fell to 10bn the following year and was down to just over 7bn by 2008-09 before bottoming out at under 6.5bn by 2009-10. But for the full year of 2010, bag use rose again to 6.8bn.

The campaign against disposable plastic bags, which green campaigners have pursued for years but which gained traction from 2006 when Wrap collated its first comprehensive statistics, enjoyed a high profile for several years. In 2007, it received a massive boost from the launch of Sainsbury's stylish cotton shopping bag from designer Anya Hindmarch, emblazoned with the legend "I'm not a plastic bag". The product – which sold for £5 in the supermarket – went on to have a lucrative after-life on eBay, reportedly changing hands for as much as £200 a time.

But while retailers say they are continuing their efforts to reduce bag use, there is less publicity around the issue.

However, in some parts of the UK, legislators are taking an interest. In Wales, shoppers will be charged 5p per bag from this October, and a consultation on charging for bags kicked off in Northern Ireland last week. Scotland shelved its proposals for a charge, but they could yet be revived.

In Wales, the imminent charge may have helped to cut bag use – the total was down by 7% last year, compared with the rise in England and Scotland. John Griffiths, Welsh environment minister, said a charge was the best way to drive down carrier use, as voluntary agreements with retailers would not achieve enough. He said: "These figures show a real difference between carrier bag use in Wales and that in other parts of the UK where no mandatory charge is planned. This proves that the carrier bag charge, which is due to be introduced in Wales on 1 October, is the only way to ensure a real and lasting reduction in the use of carrier bags."