A stretch of coastline which is one of the most important sites in the UK for seabirds such as Arctic terns and Atlantic puffins has been given greater protection.

The newly-designated Northumberland marine special protected area (SPA) stretches 12 miles from the coast into the North Sea, covering an area larger than 120,000 football pitches, government conservation body Natural England said.

The area supports 200,000 seabirds and is the most important site in the UK for Arctic, common and roseate terns, the second most important for sandwich terns and the third most important site for Atlantic puffins, Natural England said.

Designation of the SPA under the European Union birds directive builds on existing special protected areas covering seabird breeding sites at Coquet Island, Farne Islands, Lindisfarne and the Northumbria Coast.

It will help ensure disturbance to the birds’ open water feeding areas is minimised and help protect the full range of habitats the seabirds rely on, the conservation agency said.

Environment minister Thérèse Coffey said: “We already have one of the strongest track records in the world when it comes to looking after our precious marine environment, and today’s designations will strengthen our blue-belt of protected areas while helping seabirds across the country thrive.”

Andrew Sells, Natural England chairman, said the designation marked a “momentous day” for some of the UK’s best-loved and most charismatic seabirds, many of which had suffered population declines in recent decades.

“These designations will protect vital feeding areas for seabirds along the English coast, creating safe havens to help the birds thrive for generations to come,” he said.

Chris Corrigan, director of RSPB England, said: “It is fantastic to see these special places being recognised and given the protection they so need and we hope to see more designations in the very near future.

“As the UK moves closer to leaving the EU, we urge the government to continue to recognise the significance of protecting these sites, based on scientific evidence, and that they continue to protect and manage these sites to the same or even higher standards than those currently secured by European law for generations to come.”

Natural England has also announced extensions to Hamford Water SPA in Essex and Morecambe Bay and Duddon Estuary SPA in Cumbria, adding an area bigger than 150,000 football pitches to the existing marine protected area network.