Every time it rains heavily, Cllr Robert Bevan’s phone starts ringing and his social media feed is busy with people worried the coal tip that looms above the village of Tylorstown in south Wales might be in danger of slipping.

“They’re asking me: ‘Rob, is it going to happen again?’ The anxiety, the anguish is terrible,” said Bevan. “While the tip is there, even if you’ve got the best engineers working on it, you can never be sure it’s 100% safe. The tips are an albatross around our necks.”

The Welsh government is on Tuesday spelling out its requests of the UK government in this autumn’s spending review. Top of the list is a call for Boris Johnson’s administration to share responsibility for the tips and allocate long-term funding to make them safe.

It says that an estimated 40% of all UK coal tips are in Wales and about one in seven of these are classed as high risk. The Labour-controlled Welsh government argues that extreme weather caused by the climate crisis is making many of the tips unstable and believes at least GBP500m to GBP600m will be needed over the next 10 to 15 years to make them safe.

A tip above Tylorstown in Rhondda Cynon Taf partly collapsed during the storms of February last year, sending 60,000 tonnes of waste tumbling into the river close to the village’s leisure centre. It blocked part of the river valley, broke a foul sewer and wrecked a footpath and cycle path. Luckily, nobody was hurt.

After lobbying by the Welsh government, the local council and “ranting” – his word – from the Rhondda MP Chris Bryant, the UK government agreed to contribute GBP2.5m to a clear-up, a fraction of the estimated GBP18m the remediation project is costing.

“That feels measly,” said Bevan, a former mine electrician. He argued that the coal that was taken out of the valleys fuelled the whole of the UK. “The legacy of mining is still here. We’re living with it every day,” he said

Bevan said the memory of the 1966 Aberfan disaster, in which 144 people, 116 of them children, died when a junior school was engulfed in a black avalanche of slurry, coal waste and tailings from a tip, springs to mind whenever the subject is brought up. “It’s at the back of your mind when the rains come.”

This week – 20 months after the slip – workers continue to shore it up. Teams, some of them using ropes, clambered over the steep tip. Diggers and dumper trucks beavered away.

Dorothy Lewis, 80, who has run the Tylorstown village shop for half a century, said for as long as she could remember, people had debated what to do about the tips. “They used to talk about taking them down and using the material to build roads,” she said. “The problem is that it costs so much money.”

Philip Hathway, 72, a retired design engineer, paused to gaze up at the tip as he turned up for a gym session at the leisure centre. “I was a teenager when Aberfan happened. There’s still an anxiety from that all these years later.” He believes the UK government should dip into its pockets. “The whole of the UK benefited from coal,” he said.

After the Tylorstown landslip, the Welsh and UK governments set up the coal tip safety taskforce. It identified 2,144 coal tips in Wales, predominately in the south Wales valleys.

Coal tip safety in Wales is a devolved issue but the government argues the tips are a legacy of the country’s industrial history, which predates devolution.

The Welsh finance and local government minister, Rebecca Evans, is calling on the chancellor of the exchequer, Rishi Sunak to “share responsibility” and allocate funding to deal with the “pre-devolution legacy” of mining in Wales.

She said: “Climate impacts are increasing the risks disused coal tips pose to our communities. The UK government has a legal and moral responsibility to work with the Welsh government to address this issue.”

Kira Philpott’s house has a view across to the Tylorstown tip site. “It’s a bit of a mess, isn’t it?” she said, looking across the black scar in the green hill.

She lives nearby, beneath another tip. “Every time it rains hard you look up there and wonder,” she said. “If that came down we’d all really be in trouble here. We wouldn’t have a chance.”

A UK government spokesperson said: “In December 2020, to help with the unforeseen impact of Storm Dennis, we provided GBP31m of additional funding to the Welsh government, of which GBP9m was to repair vulnerable coal tips.

“Ultimately, however, the management of coal tips in Wales is a devolved matter and therefore not one the UK government would expect to provide additional funding for.”