Carphone Warehouse will open four to five electronics megastores in the UK next summer as part of its joint venture with Best Buy, the US consumer electronics giant, insisting the economic downturn was “the best time” to launch.

Best Buy raised a more cautious note, however, saying the groups would “temper” the eagerly awaited roll out, which is expected to reach 100 giant stores across Europe in the next five years, to suit the consumer slowdown.

Bob Willett, Best Buy International chief executive said the second phase of outlets would depend on economic conditions. “It’s not a race”, he added.

Carphone sold half of its retail business – encompassing 2,430 stores in Europe and the US - to Best Buy in May for £1.1 billion as part of a plan to join forces and build out around 100 megastores across the UK and Europe.

The first 30,000 sq ft outlets, which were originally expected to open by the end of the year, or early 2009, have been pushed back six months.

The jointly-owned retail arm, which will operate under the brand Best Buy Europe, is expected to sell white goods as well as consumer electronics, taking on the likes of PC World and Currys group DSG International and Kesa Electrical’s Comet stores.

In retaliation, DSG is opening its own superstore this Thursday.

Shares in Carphone Warehouse, which have more than halved since the joint venture was announced, initially rose 17p to 163p on the news, issued yesterday at 1pm London time. However, they later dropped to 136.75p, eventually clawing back some value to close down 4.44 per cent at 139.75p.

Acton-based Carphone also issued its second-quarter trading update yesterday, revealing mobile connections rose 9 per cent in the second quarter, slightly ahead of market expectations, to 3.1 million. It added 41,000 new broadband customers, on par with the first quarter.

Charles Dunstone, the group’s chief executive and founder, said he remained “extremely gloomy” about operating in the current economy, warning retailers would have to work “very hard” to get customers to part with their money in the run-up to Christmas.

The group also announced it plans to open a series of 2,000 - 3,000 sq ft shops, to be renamed “Wireless World”, which will stock televisions and gaming devices, alongside an expanded range of laptops with broadband and smart phones, including BlackBerries, the iPhone and HTC’s G1, the first mobile powered by Google’s Android platform.

The first of these mid-range stores will open at the new White City complex in Shepherds Bush at the end of this month, as the group expands its retail presence into music and TV.

Carphone said it plans to spend £90 million on the first phase of the Best Buy Europe roll out - £20 million in the current financial year to next March, with a further £30 million plus £40 million in capital spending set aside for the following year.

The group hopes to see a post tax return on investment in the mid-teens per cent by 2012. The venture will aim to double Carphone’s revenues and underlying earnings to £6.2 billion and £3.5 million respectively by March 2013.

Roger Taylor, chief executive of Best Buy Europe, and Carphone’s chief financial officer, said most of the “hundred or so” large format outlets would open in the UK, with online operations are expected to expand in mainland Europe after 12 to 24 months.

The first store will open by the middle of next year. He did not say where the outlets would be but said they were in the process of negotiating leases and hoped to sign soon.

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