The scheme, which coincides with World Oceans Day, comes as Theresa May urges leaders at a G7 summit to do more to tackle plastic pollution – describing it as a “global problem requiring global solutions”.
Under the plans, 41 new marine conservation zones around the UK’s coastline will be created to safeguard marine habitats – from Devon in the South West to Berwick on the Scottish borders.
Almost 12,000 square kilometres (7,457 square miles) of coastal waters are to be protected, with two sites in Northern Irish offshore waters.
The new zones are in addition to 50 areas which have already been earmarked for conservation as part of the Blue Belt programme.
The order bans any new activities deemed harmful, such as dredging, or significant coastal or offshore development in the designated areas and any existing harmful activities will be minimised or stopped to allow important habitats to be restored over time.
The short snouted seahorse, stalked jellyfish and peacock’s tail seaweed are among the rare or threatened marine habitats and species which will be protected.
If approved, a total of about 220,000 square km (136,701 square miles) of UK coast – two-fifths of the whole coastline – would be protected.
Environment Secretary Michael Gove, who will formally announce the plans later, said: “The UK is surrounded by some of the richest and most diverse sea life in the world. We must protect these precious habitats for future generations.
“Today marks an important step towards completing our Blue Belt. We are creating safe havens for our cherished wildlife and putting the UK at the forefront of marine protection.”
At the G7 summit in Quebec, Mrs May will call on leaders from Canada, the US, France, Germany, Italy and Japan to tackle pollution – and will claim that the UK is a “world leader on this issue”.
More from Sky Ocean Rescue
The ‘ploggers’ pick up plastic as they go running to save the world’s oceans
Tourists visiting Mediterranean Sea leaving ‘toxic legacy of plastic waste’
Sir David’s fears for marine life as plastic waste grows
Inventor hopes washing machine filter will save oceans from microplastics
Prince Charles praises Sky Ocean Rescue bid to tackle ‘global plastics plague’
Sky leads major ocean summit in Cardiff
The prime minister will say: “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.”
:: Sky’s Ocean Rescue campaign encourages people to reduce their single-use plastics. You can find out more about the campaign and how to get involved at www.skyoceanrescue.com