Campaigners are calling for tougher action to protect one of the most polluted rivers in the country after discovering raw sewage, wet wipes and plastic in the River Lea at Hackney.

They say it is a danger to humans and wildlife, and have removed thousands of kilos of rubbish from the river over the last three years. Campaigners were dismayed to see sewage after heavy flooding this year.

Celia Coram, from Save Lea Marshes, said: “There’s a lot of sewage – you can see evidence of that in the water.”

Residents say the rubbish needs to be seen as pollution and that the state of the river makes them wary of bringing children to see it as they are concerned about potential health risks.

The River Lea starts in the Chiltern Hills in Bedfordshire and joins the River Thames at Bow Creek, carrying rubbish along its way.

Environmental campaigner Julian Kirby said the river really suffered after floods in January – the worst in ten years – which dumped a lot of rubbish in the watercourse in Hackney.

“The floods left the river here in the worst state ever," Kirby said. “After the flood you could see such a ridiculous difference. It was so much worse seeing the river’s current state, it is just absolutely heartbreaking."

Volunteers from Plastic Free Hackney have been working hard to fish rubbish out of the river, using canoes to reach some of the worst rubbish.

They said they remove 100kg of rubbish every month during a two-hour pollution pick-up – that’s 3,600kg over the last three years.

Other groups also do clean-ups including Stonebridge Lock Coalition, Lower Regents Canal and Wildlife Gardeners of Haggerston.

Daisy Hutchison, from Plastic Free Hackney, said companies producing the polluting rubbish should not be let off the hook: “So there are hundreds of unpaid volunteer hours every year going into looking after the river, while the polluting water companies and plastic producers carry none of the responsibility.”

She added that the group recently started calling its clean-ups pollution picks rather than litter picks as "litter is a benign word" and focuses on individual peoples' behaviours rather than on plastic manufacturers.

Daisy called for a stronger Environment Bill which would protect the River Lea from sewage spills and make plastic producers financially responsible for the pollution they produce.

Kirby explained that many of the plastic bags washed up in the river are exempt from the plastic bag levy because they are not ones used by shops.

He also said wet wipes thrown down toilets are choking animals and causing "all sorts of health problems".

Hackney Mayor Philip Glanville said: “It’s totally depressing seeing volunteers doing this work week in and week out. We want to stop it at source.”

He said that the funding for the Environment Agency has been cut, making it harder to deal with the problem, which is not going away. Campaigners want the government to get tougher about plastic pollution.

Mayor Glanville hopes the Environment Agency will draw up a plan to tackle the problem. “We can’t go on like this,” he said.

A spokesperson for The Environment Agency said: “We share residents’ concerns about the River Lea, and we are working with our partners to improve water quality.

“We secured a £250 million investment from Thames Water to upgrade Deephams Sewage Treatment Works [in Edmonton] and improve the quality of effluent discharging into the river.

“We have also worked closely with Thames Water on the Lee Tunnel, a huge sewer pipe preventing approximately 16 million tonnes of untreated sewage from discharging into the River Lea each year.”

The government agency said it was piloting a Hertfordshire and north London "incident notification system" to tell people about incidents affecting their watercourses. It is also working with members of the London River Lea Catchment Partnership to improve the river for wildlife and people.

The spokesperson added: “Individual actions count. Many people are not aware that actions in the home can have a damaging impact on water quality. Small steps can help to protect water quality, such as not pouring fats and oils down the sink or flushing wet wipes and other plastic products down the loo.”

Watch a film about pollution on the river at www.youtube.com/watch?v=oARMNJrwkJg