PLANS to stop modern materials and buildings from damaging the character of a market town are being developed.

A study of the conservation area in Helmsley found that plastic window frames and some badly designed shop fronts were standing out from more traditional features.

The study, called Helmsley Conservation Area Appraisal, has been put together by the North York Moors National Park Authority and Ryedale District Council. It recommends that some permitted development rights should be removed so that planning permission would be needed to replace windows and doors, alter roofs and boundary fences and introduce render or painted stonework.

Owners would also have to apply to demolish outbuildings which are too small to be protected by normal conservation area controls.

A spokesperson for the national park authority, said: "This appraisal should help inform local decision makers such as property owners, the parish council, highways officers and development control officers.

"The character appraisal should also formulate proposals for the enhancement of the conservation area and, where necessary, make recommendations for the introduction of further controls to help safeguard the area's special character and sense of place. The production of this appraisal emphasises the importance placed upon retaining the historic built environment in the national park."

The document warns that there is a growing number of features that do not fit in with the character of the Helmsley.

It states: "There is an identifiable creep of the replacement of traditional features with inappropriately designed substitutes sometimes constructed of modern materials particularly along Bondgate and Pottergate.

"The most obvious are the replacement of traditionally designed timber windows and doors with plastic alternatives, the design and detailing of which bear no reference to the local vernacular.

"The future character of the conservation area is currently reliant on the education and discretion of property owners. This renders the character of the streetscape highly vulnerable."

The study is to be discussed by members of the national park authority at a meeting on Thursday.

If it is approved, it will go out for public consultation.

The authority is planning to carry out similar studies on the conservation areas in towns and villages across the national park.