The organisation said investigators documented piles of plastic dumped illegally by the roadside, in fields or spilling into waterways and floating downstream at 10 sites waste sites.
Greenpeace said plastic from the UK was found at all of these sites – with evidence of packaging and plastic bags from top UK supermarkets and retailers.
The organisation condemned British forms for dumping waste on other countries and called on Boris Johnson’s government to “take control” of the problem.
Packaging for a Covid antigen test was found amongst bags of UK plastic around Turkey’s Adana province, indicating that the waste was less than a year old.
Nina Schrank, senior plastics campaigner at Greenpeace UK, said: “It is appalling to see plastic from UK supermarkets’ shelves ending up 3,000 kilometres away in burning piles on the side of Turkish roads.
“We must stop dumping our plastic waste on other countries. The heart of the problem is overproduction – the UK is the second biggest user of plastic waste per person in the world, behind the US.”
Greenpeace called on the government to ban plastic waste exports and reducing single-use plastic by 50 per cent by 2025.
“This would not only allow the UK to end waste exports, but would also mean less plastic going into incineration and landfill,” said Ms Schrank.
Nihan Temiz Atas, a project leader at Greenpeace Mediterranean, said Turkey was being “overwhelmed” by 241 truckloads of plastic waste coming in every day from across Europe.
“As this new evidence shows, plastic waste coming from the UK to Turkey is an environmental threat not an economic opportunity,” said the project leader, based in Turkey.
He added: “Uncontrolled imports of plastic waste do nothing but increase the problems existing in Turkey’s own recycling system. As far as we can see from the data and the field, we continue to be Europe’s largest plastic waste dump.”
A Defra spokeswoman said: “We are clear that the UK should handle more of its waste at home, and that’s why we are committed to banning the export of plastic waste to non-OECD countries and clamping down on illegal waste exports – including to countries such as Turkey – through tougher controls.
“The UK is a global leader in tackling plastic pollution and our proposals for extended producer responsibility for packaging, a plastic packaging tax and mandatory electronic waste tracking will boost recycling rates, reduce waste and cut crime.”