Hundreds of demonstrators will descend on beaches and take to the sea across Scotland to protest against the planned development of the Rosebank oil and gas field.

Activists from all over the country will set out on boats, kayaks and paddleboards on Saturday to highlight their concerns over the potential impact drilling into the reservoir 80 miles north-west of the Shetland isles could have on local marine life.

Water sports enthusiasts plan to stage a paddle out in Aberdeen and leave “Stop Rosebank” messages in the sand, while in Oban campaigners from Time for Change Argyll & Bute will take part in a massive beach clean.

UK Energy Security Secretary Grant Shapps is expected to reach a decision soon on whether to approve the development of Rosebank, which is believed to be the UK’s largest undeveloped oil and gas field and thought to be capable of producing up to 500 million barrels of oil.

Campaigners estimate burning through that amount of oil would generate more CO2 emissions than 28 low-income countries produce in a year.

Dozens of climate and marine organisations, including Friends of the Earth Scotland, Surfers Against Sewage and Greenpeace UK, are demanding that Equinor, Norway’s state-owned oil company, shelves its plan to develop Rosebank and that the UK Government rejects the project.

Izzy Ross, who is joining the Aberdeen paddle out with Surfers Against Sewage, said: “I’m taking part today with surfers, divers, and others from across the UK who live by the coast to ask the Government to protect Britain’s seas and stop Rosebank.

“We are finally starting to appreciate how rich, diverse and important Britain’s waters are, and in particular the seas around Scotland.

“Now is the time to protect and restore them, not continue to pollute and industrialise them for the sake of oil and gas industry profits.

“Rosebank won’t help lower our bills, or make the UK any more energy secure, as most of its oil reserves will get put in tankers and sold overseas.

“People are demanding that our politicians put the health of our seas and amazing marine life first.”

Activists claim Equinor will have to run a gas export pipeline through the Faroe-Shetland Sponge Belt – a UK Marine Protected Area (MPA) – to develop Rosebank.

They argue this will threaten marine life on the seabed, including rare, deep sea sponges and quahogs – an endangered species of clam that can live for up to 500 years.

Campaigners say cold water coral gardens in the area could also be impacted by the development, as well as the UK’s populations of whales and dolphins.

Modelling also shows a major oil spill from Rosebank could risk serious impact to at least 16 UK MPAs, campaigners say.

Scott Herrett, just transition organiser at Friends of the Earth Scotland, who will also be taking part in the Aberdeen event, said: “Drilling for more oil and gas will cost us the earth and will continue to lock millions of people into unaffordable energy across the UK.

“It’s time for Aberdeen to go in a new direction towards clean renewable energy that has minimal impact on our marine life and can provide good quality green jobs for the long term.”

Rowan Aitchison, who is organising the Oban event, said: “We all want to be able to continue to enjoy our coast and sea in Argyll for years to come, and for future generations to be able to enjoy it and live in harmony with it too.

“For this to happen, we need to halt climate change and make sure that the oil and gas industry can’t continue to pollute our seas and damage marine ecosystems.

“The UK Government must put a stop to Rosebank and all new oil and gas projects now.”

Responding to claims made by activists during a separate protest against Rosebank in Dundee earlier this week, a spokesperson for Equinor said worst case impact assessments have been carried out to ensure the field is developed in “an environmentally responsible way”.

A UK Government spokesperson added no decision has been made regarding Rosebank yet, and that it will be the North Sea Transition Authority which ultimately decides whether to approve the field.

Meanwhile, more than 30 leading UK marine conservation organisations and campaigners have written to Labour leader Sir Keir Starmer to urge the party to hold firm on its recent pledge to end oil and gas developments in UK seas.

Led by NGOs Oceana and Uplift, the letter’s signatories highlight the overlap of oil and gas licensing with designated MPAs and ask for recognition of the cross-cutting benefits for ocean protection.