The amount of seabed litter has fluctuated over the years, but has been in long-term decline since a peak of 1,300 items per square kilometre in 2003. Statisticians link the fluctuations to weather changes, but the rise in 2016 was the first after three years of reductions.
Tim Farron, the Lib Dem spokesman on the environment, said: “It is particularly worrying to see such a sharp rise in plastic litter polluting our seas. Unless we take action, in a few years Blue Planet will have to be renamed Plastic Planet.
“The government needs to get its act together and take urgent action to clean up our seas and countryside. The long promised 25-year plan to protect our environment needs to be published now, not simply kicked into the long grass.”
The publication of Defra’s 25-year plan was originally scheduled for the summer of 2016 but has repeatedly been delayed.
Hugo Tagholm, the chief executive of Surfers Against Sewage, said the increase in seabed plastic reflected what tens of thousands of volunteers were finding along the UK coastline.
“They are seeing more and more plastic in the tideline, particularly single-use plastic, which has grown exponentially in the last two decades,” he said.
Tagholm called for taxes and policy changes to increase recycling and reduce business and supermarket use of single-use plastics. He said Defra’s current consultation on deposit-return systems for plastic bottles was crucial.
“The upstream thinking is what’s vital to protect the seabed, the water column and our beaches,” he said. “Without weaning the public off their plastic addiction we’re not going to stop this increase. We really are at a crisis point, but unlike climate change we’re at the early stages. We can stop this and reverse this trend.”
Natalie Fee, the founder of the City to Sea campaign group, said: “This is sadly yet more evidence that the tide has yet to turn against plastic pollution and all the more of an incentive to really get the solutions embedded in mainstream culture.
“Joining the Refill movement and carrying a reusable water bottle or coffee cup in public, carrying a metal straw in your bag, switching to reusable menstrual products – these things spread a powerful message, we can choose to reuse.
“We don’t have to rely on supermarkets or government to make these simple choices for us, although it would help if they were more proactive in tackling this environmental disaster.”