The new trend for natural swimming pools could help boost biodiversity across the countryside, say a couple who have applied to build one in their Norfolk garden.

If their bid for planning permission is successful, they would carry out the first study of its kind into the environmental benefits of the pools.

Swimming ponds, which have been growing in popularity in recent years, work by using a natural, biological filtration system relying on plants rather than chemicals.

The couple, named in planning papers as Mr and Mrs Brunt, have applied to build a 250 sqm natural swimming pool at their property on Back Street at South Creake, near Fakenham.

In a planning statement, they say: "The project will result in the creation of a leisure facility solely for the use of the property owners and their guests, that will also increase the visual amenity of the property, have a positive effect upon the landscape setting, and enhance local biodiversity."

It adds there has been "a significant decline" in the number of freshwater ponds, which has had "a significant effect upon local levels of biodiversity".

"Although it is estimated that Norfolk has over 23,000 surviving freshwater ponds, the number of losses across the Norfolk and Suffolk landscape have been particularly significant, with studies suggesting a 40pc decrease in the number of freshwater ponds in the region over the last seven decades."

The statement says the creation of natural swimming ponds has "a significant role to play in the enhancement of local biodiversity".

"Relying upon natural filtration beds rather than chemicals, and by specifically excluding fish from the managed aquatic environment, they become havens that bolster and increase local biodiversity," it says.

Creatures such as newts and toads would benefit from the project, while surveys would be carried out to study the benefits of the project.

The statement adds: "The Barn House Pond Project will provide significant benefits to local levels of biodiversity, and represents the first opportunity in the UK to undertake a scientific study in to the environmental benefits associated with the creation of swimming ponds, and will generate data and recommendations that will inform future projects across the region."