The South Downs has been named as the most expensive National Park in which to buy a home.

Over the last year, the area has toppled the New Forest to become the National Park with the highest average property price, according to research by Nationwide Building Society.

Spanning Hampshire and Sussex and containing around 47,000 households, the average price tag for a home in the South Downs is now £351,000, having increased by 10% over the last 12 months. Historic towns and villages in the area include Petersfield, Midhurst, West Meon, Alfriston and Petworth.

The New Forest is second on the list, with the typical home there worth £346,000, while the Lake District is in third position, with homes there costing £251,000 on average.

The "premium" that home buyers pay to live in National Parks, which are sometimes described as "Britain's breathing spaces" due to their vast expanses of open space, ancient woodlands and picture-perfect villages, has increased over the last year, according to the findings.

A property located in a National Park attracts a 21% price premium over an otherwise identical property, Nationwide found. This means that in cash terms, the premium to live in a National Park is around £39,000.

A year ago, when Nationwide conducted similar research, the percentage price premium to live in a National Park was 18%.

Robert Gardner, Nationwide's chief economist, said: "Around 190,000 households in Great Britain are located within the boundaries of National Parks, and our research suggests that this factor alone attracts a significant price premium."

He continued: "National Parks are highly desirable areas in which to live thanks to the beautiful countryside.

"Development is also strictly controlled, with very little in the way of new housing construction, which also helps to explain why prices are relatively high."

As prices are being driven up within National Parks, there are also knock-on effects on the property values in surrounding areas.

Nationwide found that homes situated within five kilometres or around three miles of a National Park command an 8% premium compared with similar properties outside of this range. This percentage is unchanged from last year.

Snowdonia remains the least expensive National Park in which to buy a home, with average property prices there at £138,000. But it has seen the largest price jump over the last year out of the National Parks looked at, with property values there increasing by 16%.

Other National Parks which have seen double-digit house price increases over the last year include the Brecon Beacons, where values have lifted by 12%, and the Peak District, where they have recorded an 11% increase.

Mr Gardner said that of the National Parks looked at, the Peak District serves the highest number of people, with a population of around 5.9 million living within 25km of its boundary.

He said: "Its central location makes it accessible from major population centres such as Derby, Sheffield and Manchester."

The Lake District was the only National Park in the study where house prices have slipped back compared with a year ago. Values there have recorded a 1% annual fall.

Loch Lomond and the Trossachs have seen house prices lift by 9% over the last 12 months, while property values in the Cairngorms have increased by 2%.

Mr Gardner continued: "The Cairngorms is the largest National Park by land area, but is located within a very sparsely populated part of Scotland.

"Loch Lomond and the Trossachs are closest to major cities such as Glasgow and Edinburgh, with 1.1 million people within 25km."

Nationwide used data from its own database for the findings. Some National Parks were excluded due to low sample sizes. These were The Broads, Exmoor, Northumberland, the North York Moors, the Pembrokeshire Coast and the Yorkshire Dales.