Double council tax on unsellable property

[Fearless Dog]

My 90-year-old mother pays £146 per month to the East Riding of Yorkshire Council for a small seaside bungalow on the Holderness coast. This is a second home and is used for approximately five months of the year. It stands barely ten metres from the cliff edge and is subject to coastal erosion. The council has confirmed that from April of 2025 the council tax will double. She already receives no services from the council - bins are not emptied; there is no street lighting and no tarmac on the road. She cannot sell the property because no one would buy it given that she will be served with a compulsory eviction notice once there is less than 9.36m of cliff remaining. The council is fully aware of her situation, but have stated they will make no exceptions to the new ruling. So there we have it - my mum will be forced to pay double council tax (which she cannot afford) on a property she cannot sell. Can this be legal?