One MEP claimed that if no action was taken against plastic pollution "by 2050 there will be more plastic than fish in the ocean".
Researchers from the World Wildlife Fund (WWF) and the park's conservation academy uncovered more than 1,000 other pieces of plastic, including 115 plastic cups, four plastic bottles, 25 plastic bags, 2 flip-flops and a nylon sack.
The items were part of almost six kilograms (13 pounds) of plastic waste discovered in the 9.5-metre (31-foot) carcass when it washed ashore in Wakatobi National Park, in Southeast Sulawesi province, on Monday.
A photo of the materials found inside the whale posted by the WWF shows a teeming mound of garbage, including a tangle of what appears to be string and a broken piece of a plate.
The exact cause of the whale's death is not yet known but there are signs that "plastic waste might have triggered it", WWF Indonesia marine species conservation coordinator Dwi Suprapti told AFP.
The 9.5-metre (31.17 ft) whale was found in waters near Kapota Island, part of the Wakatobi National Park, south east of Sulawesi, the park said in a statement.
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It wasn't possible to determine if the plastic was responsible for the death because of the advanced state of decay.
Five Asian nations - China, Indonesia, the Philippines, Vietnam and Thailand - account for up to 60% of the plastic waste that ends up in oceans, according to a 2015 report by environmental campaigner Ocean Conservancy and the McKinsey Center for Business and Environment.
Plastic pollution is a worldwide problem, but it's particularly bad in Asia, where there are few collection and recovery systems. The country creates more than three million tonnes of mismanaged plastic waste every year. Unfortunately, only half of that trash reaches landfills.
Luhut Binsar Pandjaitan, Indonesia's coordinating minister for maritime affairs, told the AP that he sees plastic waste as a "common enemy".
"I'm so sad to hear this", said Pandjaitan, who recently has campaigned for less use of plastic. He vowed that the government would bolster its efforts to stop plastic from reaching oceans in the near future.
'It is possible that many other marine animals are also contaminated with plastic waste and this is very risky for our lives'.