Almost 300 old coal tips in Wales have been classed as “high risk” a year on from a 60,000 tonne landslip caused by Storm Dennis.
The matter will now be discussed at a Welsh Government summit on mine safety on Tuesday.
There are more than 2,000 coal tips in Wales. Most are on private land and most are around south Wales’ valleys.
Of those, 294 are categorised as “high risk”, meaning they could endanger life or property.
Seventy are in Caerphilly, 64 in Rhondda Cynon Taf, 59 in Merthyr Tydfil, 42 in Bridgend, 35 in Neath Port Talbot, 16 in Carmarthenshire and eight in Swansea.
The landslip last year was at Tylorstown, in Rhondda. Since it happened, work has been done to map tips and assess their stability.
The Welsh and UK governments, the coal authority, local authorities and other bodies have been examining the problem.
Their investigation has concluded current legislation surrounding tips is “neither sufficiently robust or fit for purpose in relation to inspection and maintenance”.
Coal Authority chief executive, Lisa Pinney, said managing tips on hillsides is key to reducing risk to communities.
“Just under 300 are higher risk sites but that really just means that they needed much more regular attention and inspection to make sure they stay safe,” she said.
She said when there were concerns, action would be taken.
“Any tip which is old mining material sitting on a hillside can pose a risk, obviously, but the key thing to their safety is to manage water and keep it away,” said Ms Pinney.
“And that’s why these inspections and maintenance are so important.”
No one was hurt in the Tylorstown landslip and work is under way to secure the hillside.
Rhondda MP Chris Bryant said funding was essential.
“It’s shocking that no proper register of disused coal tips was made when the mines closed, so this work is long overdue,” he said.
“With so many on private land this is going to be a massive and complex piece of work in which parliament and Senedd must work together.
“My biggest fear is [Chancellor] Rishi Sunak will demand that local councils pay for this out of their council tax but the poorest communities in the UK should not be forced to pay for tidying up our national industrial heritage.”
Coalfield historian Dr Ben Curtis said some tips were removed or made safe after the Aberfan disaster in 1966.
“But it is a potential problem that continues to remain for some of these tips to become unsafe over time, perhaps (because of) factors like the effects of climate change and increased rainfall,” he said.
The summit – which will be held virtually – is also expected to discuss wider issues of mine safety after water escaped when it built up in a mine shaft in Skewen, Neath Port Talbot, flooding nearby homes in January.
A UK government spokesperson said: “Ever since the devastating storms of early 2020, the UK government has been working with the Welsh Government on its devolved responsibility to provide extra support for flood relief and protection to the communities which were so badly affected.
“In December we confirmed that £31m would be provided for this vital work, of which £9m was to repair vulnerable coal tips.
“We also provided the Welsh Government with an additional £1.3bn for next year at the recent spending review so they are well placed to continue this work”