The shares dropped 6½p to 303½p yesterday, following Thursday’s 13 per cent tumble, as City analysts digested the impact of this week’s loss of a key contract with Vodafone.

But Carphone Warehouse sought to win round investors concerned about the damage caused by Vodafone’s departure, maintaining its other key customers would remain loyal.

The group said that O2 and T-Mobile — two of its key customers — had agreed to continue their relationship.

However, the assurances from Europe’s biggest independent mobile retailer failed to win over some analysts who said that the departure of Vodafone — and the threatened departure of Orange, another key client — had thrown into doubt the group’s retail strategy.

Analysts at Morgan Stanley said in a note that Carphone Warehouse’s “entire retail business model could be undermined not only in the UK but across Europe” if Vodafone’s strategy to push contract phone sales through Phones 4U, Carphone Warehouse’s rival, worked. Analysts estimated that Vodafone could save 20 per cent of the cost of signing up each contract customer under the deal it negotiated with Phones 4U.

Merrill Lynch said in a note that it believed that Orange and O2 could attempt to turn the screws on the retailers.

However, O2 said in a statement that Carphone Warehouse would continue to “play an important part in our distribution strategy”.

Chains such as Carphone Warehouse and Phones 4U receive chunky commissions from each contract sold. In addition they often receive a continuing share of the revenues generated by the customers calls. But as the market has matured the main mobile networks such as Vodafone and Orange have been forced to review the economics of acquiring customers.

They have all sought to cut back on sales done through these middlemen and instead sell more phones directly through their own branded stores and through their websites.

Sean Collins, managing director of Collins Consulting, said: “The mobile operators are seeking to regain control.”

The move by Carphone Warehouse to become a telecoms player in its own right has also irked some of its clients. “It is essentially using the profits it makes from us to pump into products to rival ours,” one industry source said. For example, Carphone Warehouse and Orange went head to head in the recent auction for the UK arm of AOL, Time Warner’s internet business, and both are aggressively marketing “free” broadband services.

Charles Dunstone, the chief executive of Carphone Warehouse, is understood to have been stunned by the Vodafone announcement and the timing of it, which came just as the group was celebrating winning the auction for the British arm of AOL.

Vodafone, which is reviewing its pre-pay contract with Carphone, was the retailer’s first customer when it was set up.

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