14 new marine conservation zones have been designated in and around the South West Coast.
The UK's added a total of 41 additional protected marine spaces to the Blue Belt programme.
Morte Platform South West
North-West of Lundy
Approaches to Bristol Channel
South of the Isles of Scilly
Devon Avon Estuary
East of Start Point
South of Portland
Prime Minister Theresa May will tell the G7 summit that plastic pollution in the oceans is a "global problem, requiring global solutions".
As part of World Oceans Day the new zones will protect rare or threatened marine habitats and species including the short-snouted seahorse, eider ducks, stalked jellyfish and peacock's tail seaweed.
No new activities deemed damaging - such as dredging, or significant coastal or offshore development - will be allowed, while existing harmful activities will be minimised or stopped.
There is an urgent need for greater global action and co-ordination on marine plastics pollution, including working with business, industry and non-governmental organisations to find innovative and effective solutions.
The 41 proposed new MCZs follow the 50 already announced as part of the Blue Belt programme.
The new zones cover approximately 11,700 square kilometres, bringing the total area of protection to over 32,000 square kilometres.