As shares in Vodafone hit a three-year low in afternoon trading, some investors suggested that Mr Sarin could face “crunch time” at the company’s annual meeting in July.

“These markets are competitive but it is the job of management to beat that competition,” said one major shareholder, who did not wish to be named. “Good management makes its own luck.”

Vodafone’s decision to cut the book value of its assets by between £23 billion and £28 billion was blamed mainly on the company’s German operations, a result of its record €178 billion hostile takeover of Germany’s Mannesmann in 2000. However, Vodafone admitted that its businesses in Italy and potentially Japan had also contributed to one of the biggest ever postacquisition writedowns.

Vodafone said recent price competition in mature markets and the threat from new technologies, such as internet telephony, had triggered a cut to its long-term growth assumptions.

The group predicted that mobile phone revenue growth for 2007 would be between 5 and 6.5 per cent. It has already estimated that 2006 growth would be 6 to 9 per cent. Previously the group had forecast “slightly lower” revenue growth next year.

Vodafone shares closed 3¼p lower at 113¾p.

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