Urgent action must be taken to stop the derelict Assize Courts from deteriorating further, Devizes town councillors have told Wiltshire Council.

The crumbling grade II listed building in Northgate Street has been standing empty for 25 years while schemes to convert it have failed to materialise.

Planning permission was granted 18 months ago to owners Gatewell, based in the Bahamas, to convert the building to 18 flats while the central lobby would be for community space but no work has been carried out.

On Tuesday night Devizes Town Council’s planning committee agreed to request Wiltshire Council to survey the Assize Courts to determine what work is needed to be undertaken on it to prevent further deterioration.

If the owner fails to act promptly, councillors in Devizes want Wiltshire Council to carry out the work itself and charge the owner.

Town councillor Ted East, who proposed the recommendation and who went inside the Assize Courts a year ago, said: “It is the second winter since planning approval was given to convert the Assize Courts into flats. The inside is in an appalling state.

“All the valuable original features have been destroyed by theft and vandalism. The wooden parquet flooring has been destroyed by squatters lighting fires on the floor and iron railings have gone.”

Town councillor Sue Evans, also a Wiltshire councillor, read out a statement she had been given by Wiltshire Council’s conservation department which said the council continues to monitor the condition of the Assize Courts and reminds the owner’s agent of the benefit of taking steps to secure the building.

The statement added: “Whilst it is regrettable that no significant progress has been made they have at least been co-operative in responding to some small issues, although we are aware of the gradual overall deterioration.”

It also claimed that there had been no recent fundamental change in the state of the building which could be addressed by works initiated by the council.

Town councillors were not satisfied by Wiltshire Council’s response and called for action. Coun East and Coun Nigel Carter even thought a compulsory purchase order should be considered.

Coun Carter said Wiltshire Council and the town council were held in contempt by people over the state of the Assize Courts, which he described as “a festering sore”.

Coun Jane Burton said: “The place is falling into disrepair. What price do you put on a listed building? If it falls down you don’t get it back.”

The Gazette tried to contact Gatewell agent Martin Henneberry of Urban Spectrum yesterday but was told he was out of the office. A colleague said he would pass on our request to speak to him.