Councillors have warned the owner of Worthing's most historic building: "We are coming to inspect your property whether you like it or not."

The ultimatum came at a meeting of the borough council's executive as patience finally ran out over Castle Goring, a Grade I listed building on the outskirts of town.

Experts will now demand access to the 16th century country house, which is owned by the Somerset family.

And landowner Clem Somerset has been told the council may have to compulsorily purchase the property if its demands are not met.

The council took action amid growing concern from conservation watchdogs about the condition of the building, built in 1797-1798 by Sir Bysshe Shelley.

Natalie Cropper, speaking for the Worthing Society said: "We feel very strongly about it. This is a scandalous situation and we should be able to stem the decay."

The building, which is partly occupied by a language school, was in 2002 placed on English Heritage's "at risk" register, which warned the building was in immediate danger of further rapid deterioration.

Clare Mangan, the council's strategic housing and planning manager, said: "Castle Goring is a Grade I-listed building, one of only two in the borough."

"In 2002, Castle Goring was placed in category A of English Heritages at risk register. The condition of the building is described as 'very bad.'

"Over the past three years the council has made various attempts to gain access to the building to ascertain its condition and was successful in viewing the majority of the building in September 2001.

"However, on this occasion, two areas of the building were not accessible and despite numerous attempts to arrange a further visit, there has been no response from the occupier.

"It was clear from the visit in 2001 that there was cause for concern regarding the future of the building, which has been neglected for some time.

"Given the risk to a building of historical and architectural importance, the council must consider whether it is now appropriate for it to adopt a more formal approach to secure entry to the building and ensure its long term future."

The executive agreed with a recommendation that access should be sought with a view to serving a repairs notice, action that would cost the council £6,000.

Coun John Lovell, deputy leader of the council said: "I find it difficult to stomach the fact that we have to pay to look at a house that belongs to somebody who is very rich."

Mr Somerset said: "Castle Goring is let to a tenant under a full-repairing lease. The building is watertight as far as I know.

"There are always problems with the dome in the centre. To get Castle Goring back as it was would be totally beyond any individual's means as far as I am concerned. It would be out of the question."

The south frontage of Castle Goring has a Roman-style facade, while the north frontage is Gothic in design.