Experts from the Scottish Marine Animal Stranding Scheme, which investigates the deaths of whales and dolphins, said there was no evidence that the 100kg “litter ball” had “impacted or obstructed the intestines”.
But they said the discovery of so much plastic pollution in its stomach was “nonetheless horrific”, and most likely “compromised digestion”.
“This amount of plastic… serves to demonstrate, yet again, the hazards that marine litter and lost or discarded fishing gear can cause to marine life,” the group added.
The ball was made up of land and fishing waste and could have been consumed by the whale at any point between Norway and the Azores.
The number of cetaceans being stranded on UK shores has risen, with 1,000 whales, dolphins, and porpoises found washed up in 2017 alone.
Figures from the UK Cetacean Strandings Investigation Programme (CSIP) reveal that a total of 4,896 animals died on beaches between 2011 and 2017, a 15 per cent increase compared to the previous seven years.
On Friday, a minke whale washed up in the River Thames under Battersea Bridge, the second to be found dead in two months after a humpback whale was found dead in Greenhithe in October.