Marine litter presents a global problem, with increasing quantities documented in recent decades. The distribution and abundance of marine litter on the seafloor off the United Kingdom's (UK) coasts were quantified during 39 independent scientific surveys conducted between 1992 and 2017. Widespread distribution of litter items, especially plastics, were found on the seabed of the North Sea, English Channel, Celtic Sea and Irish Sea. High variation in abundance of litter items, ranging from 0 to 1835 pieces km−2 of seafloor, was observed. Plastic tems such as bags, bottles and fishing related debris were commonly observed across all areas. Over the entire 25-year period (1992–2017), 63% of the 2461 trawls contained at least one plastic litter item. There was no significant temporal trend in the percentage of trawls containing any or total plastic litter items across the long-term datasets. Statistically significant trends, however, were observed in specific plastic litter categories only. These trends were all positive except for a negative trend in plastic bags in the Greater North Sea - suggesting that behavioural and legislative changes could reduce the problem of marine litter within decades. Marine litter abundance (litter items km−2) on the seafloor in North West European Seas, all data from 2011 interpolated using R, Shiny and PostGIS. The black line surrounding the UK represents the 12nm boundary. The black line in the Western Channel and starting near the tip of Shetland symbolizes the MSFD boundary for the Celtic Sea (CS) and Greater North Sea (GNS). Key to regional divisions: GNS-off, Greater North Sea offshore stations outside 12nm; GNS-in, Greater North Sea inshore stations within 12nm; CS-off, Celtic Sea offshore stations outside 12nm; CS-in, Celtic Sea inshore stations within 12nm. Display omitted •Widespread distribution of litter items on the seabed, up to 1835 pieces km−2•Over the 25-year period, 63% of the trawls contained at least one plastic litter item.•No significant temporal trend in total number of litter items km−2•Significant trends in plastic bags (down) and fishing debris (up)•Potential influence of behavioural changes on litter abundance?