Tough new controls will stop homeowners from "spoiling" Brighton and Hove conservation areas.

The city council is introducing the measures in four conservation areas to prevent ugly alterations being carried out on Georgian and Victorian homes without planning permission.

A six-month trial in streets around Preston village, Preston Park, Roundhill and West Hill was today extended when the council enforced the controls indefinitely.

A survey showed many homeowners had carried out changes such as converting front gardens for parking, installing double glazing and replacing slate roof tiles with other materials.

The directive will apply to the front of homes in the four conservation areas which have so far escaped controls already imposed on properties converted into flats.

Council senior planning officer Lesley Johnston said: "Under current planning controls there is a certain amount of permitted development allowed without planning consent.

"Over time small changes can have a cumulative effect and we want to protect the character of these four conservation areas."

The council is also considering introducing the controls in the Regency and Clifton Hill areas.