The legislation is the 1990 Planning (Listed Buildings and Conservation Areas) Act. In taking enforcement action, a local authority will consider the policy guidance contained in a document called ‘PPG 15: Planning and the Historic Environment’. Local authorities have “powers to take action where a historic building has deteriorated to the extent that its preservation may be at risk”. This is only likely to happen if a listed building is allowed to fall into a very bad state.

Then there are two other possibilities:

An Urgent Works Notice: This is for unoccupied buildings, or parts not in use. It should involve the minimum urgently needed to put the building in a sound and weathertight condition. If the work is not done the authority can enter the land and complete the work by default having given 24 hours’ notice.
Repairs Notice: This involves more extensive work, and it is generally taken that the building should be put back into its condition at the time of listing, or otherwise into a reasonable state. A Repairs Notice is technically a preliminary step towards compulsory purchase, although local authorities usually see it as a last resort.