Images have been released by xo168 London's Royal Parks to show the impact of litter on wildlife.
Plastic bags, party balloons and plastic beer pack rings were found on animals in the parks last year, while some habitat was destroyed by fires from barbecues.
Litter weighing the equivalent of 157 double-decker buses was collected between April 2020 and April 2021.
It costs an average of £1.3m a year to clean the eight Royal Parks.
A plastic bag tightly wrapped around a stag's mouth, a hedgehog caught on film entangled in a party balloon and a cormorant with a plastic beer-pack ring round its neck were among the most distressing images, the charity said.
"Taking that moment to decide to clear away a bottle or small piece of plastic rather than leaving it behind could make all the difference to the lives of the parks' wonderful wildlife." said Tom Jarvis, director of parks.
"Sadly, we've all too often seen the devastating impact that dumping litter, leaving barbecues smouldering or treading into protected areas of the parks can have on the environment and wildlife."
Throughout the different lockdowns and beyond, huge amounts of litter have been cleared, including plastic bags filled with left-over picnic waste, pizza boxes, glass bottles, dog poo bags and PPE.
"We work round the clock to keep the parks beautiful, safe places for everyone to enjoy, but keeping the parks litter-free comes with a huge price tag," Mr Jarvis added. "This is time and money that could be better spent on preserving the natural environment."