A purple potato that growers claim contains greater health benefits than the average white variety goes on sale today.

The Purple Majesty has a deep purple skin and flesh and contains nine to 10 times more antioxidants than standard potatoes, according to Scottish producer Albert Bartlett.

The potato was bred from a traditional variety by scientists at Colorado University, but trials over the last two years found it could be grown in Scotland.

An initial "smallish" crop of 400 tonnes goes on sale this week across the south east of England and Scotland, with a larger yield expected next year.

Gillian Kynoch, head of product development and innovation at Albert Bartlett, said tests found the potatoes to be high in anthocyanins, the pigment found in other purple fruits and vegetables including grapes, blueberries and red cabbage, which acts an an antioxidant.

Blood tests on people who had eaten the potatoes found the health benefits were retained throughout the cooking process.

She said: "This potato packs a powerful nutritional punch while tasting as delicious as more familiar varieties.

"They perform beautifully in the kitchen, mashing, baking, roasting and microwaving to perfection, and make spectacular chips and crisps."

Sainsbury's is selling the potatoes for £1.50 for 1.25kg.

Liz Jarman, head of product technology at Sainsbury's, said: "Purple Majesty is set to change how the public view potatoes. Until now they have always been viewed as white, reliable - but predictable. But no longer.

"We're expecting sales to peak over Halloween because purple mash, crisps and wedges will be a ghoulish treat at children's parties."