The £600 million needed to make Wales' coal tips safe over the next 15 years, should be a responsibility shared by Westminster, the Welsh government has said.
It is estimated 40 percent of all the UK's coal tips are in Wales and around one in seven are classed as high risk.
The Welsh Government has said that at least £500m to £600m is needed over the next 10 to 15 years to prevent future landslips.
One of the most famous landslips was the Aberfan disaster In October 1966.
116 children and 28 adults were killed when a mountain of coal waste collapsed on the village's school in the South Wales valleys.
Wales' Finance and Local Government Minister Rebecca Evans, says that the UK Chancellor, Rishi Sunak should use the Autumn Spending Review to announce funding for the project.
"Wales is disproportionately affected by the legacy of coal mining, and climate impacts are increasing the risks disused coal tips pose to our communities.
"As a pre-devolution issue, we need the UK Government to share responsibility and prevent another landslip from happening.
"As rainfall intensifies and temperatures rise, the risk to life and livelihoods is increasing unpredictably.
"The UK Government has a legal and moral responsibility to work with the Welsh Government to address this issue and fund these long-term costs.
"There is an opportunity for us to work together in the coming years to tackle the climate and nature crisis we face and this year's Spending Review is the chance to find that common ground and to leave a positive, fairer and lasting legacy for former mining areas in Wales."
A UK government spokesperson said: "In December 2020, to help with the unforeseen impact of Storm Dennis, we provided £31m of additional funding to the Welsh government, of which £9m 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.
"The Welsh Government is more than adequately funded to manage the costs of devolved responsibilities.
"Their 2021-22 spending review settlement provides around £123 per person for every £100 of equivalent funding in England. This is around £1 billion more than the agreed level of fair funding for Wales relative to England as set out in the fiscal framework."
The Autumn Spending Review will set the amount of funding available to the Welsh Government for the next three years to 2024-25. It will be announced alongside the autumn budget on 27 October.