Shares in Britain's Dixons Carphone have dived as much as 30% after the retailer cut its full-year profit forecast, blaming tougher conditions in the mobile market as customers keep their handsets longer.

Dixons Carphone - which trades as Currys, PC World and Carphone Warehouse in Britain and Ireland - said the weakness of the pound was also making new devices more expensive at a time when technical innovation has been limited.

A market leader in both the electricals and mobile phone market, Dixons Carphone said headline pretax profit for the year was expected to be in a broad range of £360m to £440m.

The group reported profit of £501m in the year to 29 April, and analysts had expected a similar number this year.

On average they had forecast £495m, according to Thomson Reuters data.

Chief Executive Seb James said customers were taking their time before upgrading their phones to the latest model.

"The cause of that really is that people are holding on to handsets longer, on average we are seeing four to five months longer," he said.

The shares traded 24% lower at 179p at 10.45am Irish time.

They had already fallen by a third this year as investors feared Britain's biggest electricals retailer would suffer from the growing inflationary pressures on consumers.

Analysts said the fact the group was trading well in its electricals business, which sells more expensive items, suggested the problem had its roots in a lack of innovation in the mobile phone market.

"Unfortunately that's not something Carphone Warehouse can do a great deal about," said Nicholas Hyett, equity analyst at Hargreaves Lansdown.

"The forthcoming generation of Samsung Galaxy and iPhone handsets claim to make big steps forward, but recent history hasn't delivered much that's revolutionary. Seb James will be hoping (Apple boss) Tim Cook has something big up his sleeve."

Strong growth for Irish market

Despite the UK performance, Dixons Carphone Ireland (Currys PC World and Carphone Warehouse) said it continues to perform strongly here, with like-for-like sales growing - especially across consumer electrical goods.

Managing Director of Dixons Carphone Ireland Mark Delaney said: "Carphone Warehouse continues to grow market share in the Irish mobile market.

"We are adding more customers on a first-time connection basis. In a growing market, Carphone Warehouse has already capitalised on Irish consumers increasing their smartphones usage.

"With the launch of iPhone 8 and Samsung Note 8, coupled with upcoming crucial sales periods, we would expect further growth as we see Irish consumers adopt these new phone upgrades."

He added: "In Ireland consumer confidence remains buoyant and we are optimistic in the ability of Currys PC World and Carphone Warehouse to capitalise on the many opportunities that lie ahead and we continue to innovate and invest."