Chemicals leach into the water, and it has been shown that even humans who eat seafood ingest 11,000 pieces of microplastic each year.
Prince Charles, long known for his interest in environmental causes, was attending a meeting of the International Sustainability Unit (ISU) which he established in 2010 to help tackle issues such as deforestation, climate change and marine health.
"Over the last few years, the awareness and science about the negative impacts of plastic waste in our ocean have grown significantly," he added.
"Many of you, I know, shared my deep frustration that the world was seemingly just turning a blind eye to this mounting evidence.
"Thankfully, the level of concern has now changed, not least because of your efforts.
"Even though the challenge at hand is extremely grave and unbelievably urgent, I for one at least find some encouragement from the fact that the legacy of plastic in the environment is now very much on the global agenda and in the public consciousness."
At the meeting, he praised collaborative and integrated efforts to solve the problem of plastic waste.
He said: "In a culture where the forces of competition so often swamp the imperative of co-operation, breaking out of the silos that slow down progress is even more of an achievement."
Attendees at the "Keeping plastics and their value in the economy and out of the ocean" conference included representatives from the Ellen MacArthur Foundation, Marks & Spencer, Waitrose, PepsiCo UK, and Sky Ocean Ventures Fund.
Reacting to today’s speech by The Prince of Wales on plastic pollution, Friends of the Earth chief executive Craig Bennett, who attended the meeting, said:
“The Prince of Wales has been championing the environment for decades, so we’re delighted he is bringing his considerable influence to tackle the scourge of plastic pollution.
“We share the Princes’ frustration at the slow pace of action on this issue.
“Theresa May rightly recognises the need to act – but speedier efforts are needed to slash waste, boost recycling and stop the tsunami of plastic pouring into our oceans.”