British seas are being treated “like a sewer”, polluted by an endless stream of plastics, untreated waste and farming effluent, MPs have warned.

In a damning new report, the Environmental Audit Committee has laid out the dangers facing the nation’s oceans and what needs to be done to address them.

Besides pollution, climate change, overfishing and deep sea mining are all threatening marine ecosystems and the trillions of pounds they deliver to the economy, the report states.

The UK is responsible for an area of ocean roughly 30 times the size of the country itself, but the committe accused ministers of “sea blindness” when it comes to tackling marine environmental problems.

Besides taking action to protect its national waters, it said Britain should leverage its international clout to push for a legally-binding “Paris agreement for the sea”.

Urgent domestic action will also be necessary, with more ambitious targets both to achieve zero avoidable plastic waste and to completely decarbonise the economy in a bid to avert devastating climate change.

“Our children deserve to experience the wonders of the ocean but climate change poses a triple whammy of threats from ocean warming, deoxygenation and acidification, which are decimating marine life,” said committee chair and Labour MP Mary Creagh. “The government’s ‘out of sight, out of mind’ attitude on the seas must change.”

More than 80 per cent of the pollution that ends up in the sea comes from the land, and the MPs called for more stringent measures to cut off this flow.

These included bans on unrecyclable plastic packaging and legally binding targets for water quality to cut chemical pollution draining into the seas.

Plastic waste across the world: in pictures Show all 15 1 /15 Plastic waste across the world: in pictures Plastic waste across the world: in pictures A father and son on a makeshift boat made from styrofoam paddle through a garbage filled river as they collect plastic bottles that they can sell in junkshops in Manila. The father and son team earn some three US dollars a day retrieving recyclables from the river. AFP/Getty Plastic waste across the world: in pictures A composite image of items found on the shore of the Thames Estuary in Rainham, Kent. Tons of plastic and other waste lines areas along the Thames Estuary shoreline, an important feeding ground for wading birds and other marine wildlife. Getty Images Plastic waste across the world: in pictures Children collect plastic water bottles among the garbage washed ashore at the Manila Bay. According to the United Nations Environment Programme, at current rates of pollution, there will likely be more plastic in the sea than fish by 2050. AFP/Getty Plastic waste across the world: in pictures Plastics and other detritus line the shore of the Thames Estuary. In December 2017 Britain joined the other 193 UN countries and signed up to a resolution to help eliminate marine litter and microplastics in the sea. It is estimated that about eight million metric tons of plastic find their way into the world's oceans every year. Once in the Ocean plastic can take hundreds of years to degrade, all the while breaking down into smaller and smaller 'microplastics,' which can be consumed by marine animals, and find their way into the human food chain. Getty Plastic waste across the world: in pictures A dump site in Manila in 2013. The Philippines financial capital banned disposable plastic shopping bags and styrofoam food containers, as part of escalating efforts across the nation's capital to curb rubbish that exacerbates deadly flooding. AFP/Getty Images Plastic waste across the world: in pictures Children swims in the sea full of garbage in North Jakarta, Indonesia. Getty Plastic waste across the world: in pictures An Indian woman holds a jar filled with Yamuna river water polluted with froth and toxic foam to be used for rituals at the river bank in New Delhi, India. The Yamuna River, like all other holy rivers in India, has been massively polluted for decades now. The river that originates in a glacier in the pristine and unpolluted Himalayas, and flows through Haryana, Delhi and Uttar Pradesh before merging with the Ganges River in Allahabad, once used to be the lifeline of the Indian capital. Currently, it is no more than a large, open sewer that is choking with industrial and domestic discharge that includes plastic, flowers and debris and has virtually no aquatic life. EPA Plastic waste across the world: in pictures Plastic waste is washed up on South Troon beach in Scotland. Recent reports by scientists have confirmed, plastics dumped in the world oceans are reaching a dangerous level with micro plastic particles now being found inside filter feeding animals and amongst sand grains on our beaches. Getty Plastic waste across the world: in pictures Children collect plastic to be sold and recycled, in a polluted river in suburban Manila. The city's trash disposal agency traps solid waste floating down waterways that was thrown into the water by residents of slums along riverbanks upstream. AFP/Getty Plastic waste across the world: in pictures View of the Carpayo Beach in La Punta, Callao, some 15 km of Lima. In 2013, the NGO VIDA labeled the Carpayo Beach as the most polluted in the country - 40 tons of trash on each 500m2. AFP/Getty Plastic waste across the world: in pictures Trash from Kamilo Beach in Hawaii. Gabriella Levine/Flickr Plastic waste across the world: in pictures A scavenger collects plastic cups for recycling in a river covered with rubbish near Pluit dam in Jakarta. Reuters Plastic waste across the world: in pictures Rubbish fills Omoa beach in Honduras. Floating masses of garbage offshore from some of the Caribbean's pristine beaches are testimony to a vast and growing problem of plastic pollution heedlessly dumped in our oceans, locals, activists and experts say. AFP/Getty Plastic waste across the world: in pictures A man climbs down to a garbage filled river in Manila. Plastic rubbish will outweigh fish in the oceans by 2050 unless the world takes drastic action to recycle the material, a report warned in 2016. AFP/Getty Plastic waste across the world: in pictures Garbage on East Beach, Henderson Island (Pitcairn Islands), in the south Pacific Ocean. The uninhabited island has been found to have the world's highest density of waste plastic, with more than 3,500 additional pieces of litter washing ashore daily at just one of its beaches. EPA

“Our government has repeatedly stated its desire to lead the world in ocean protection, and this report outlines exactly how to do that,” said Will McCallum, head of oceans at Greenpeace UK.

As well as cutting plastic, Mr McCallum said “strong international leadership” on marine issues like Antarctic Ocean sanctuaries would be vital.

Previous efforts to protect areas of the ocean such as the Weddell Sea have proved unsuccessful, suggesting a more concerted global effort is required.

Project to clean up the "Great Pacific Garbage Patch" unable to collect plastic

A network of non governmental organisations known as the High Seas Alliance has been campaigning for a Paris agreement-style deal that would have the power to create and protect huge marine protected zones.

The committee said the government should mobilise the highest levels of government, including the foreign secretary, and the UK’s position as chair of the Commonwealth to push for these measures.