BAE Systems, the British defence group, is preparing to send in a team of independent auditors to carry out a valuation of Airbus Group, the beleaguered jet maker, in which it holds 20 per cent and is considering selling the stake.

The move is a clear challenge to the €2.75bn valuation put on the stake by Rothschilds, the independent investment bank. Analysts have put the value at €4 billion.

It is understood that negotiations with an outside auditor are at an advanced stage although a deal has yet to be fully agreed. However, BAE will be keen to stress the independence of its own valuation of Airbus, which it may be able to use to negotiate a better price.

BAE, which has been shocked by the Rothschild's valuation, has still not decided whether to press ahead and exercise a put option it has over the Airbus, after damaging revelations emerged about delays in delivering its new A380 super-jumbo.

The delays have wreaked havoc at EADS, parent company of Airbus, and cost the jobs of the joint chief executive Noel Forgeard and the head of Airbus itself, Gustav Humbert. EADS shares have tumbled nearly a third since mid-June when it revealed the delays, which are expected to hit its pre-tax profits by €500 million between 2007 and 2010.

Either way, the audit as unveiled today will delay the original timetable. BAE had hoped to complete the sale by the end of this month. However, the audit is expected to take about six weeks to complete, meaning an emergency meeting and a shareholder vote will be unlikely before early September.

The Rothschild's valuation is binding on EADS, but not on BAE Systems.

BAE's own auditor is KPMG, while both KPMG and Ernst & Young are auditors to EADS. It is not which company acts as auditor for Airbus.

Shares in BAE, which tumbled after news of the Rothschilds valuation emerged over the weekend, fell 4.25p to 351.25p in a wider market that was dropping steeply.

For full details of the shares click here

Should BAE decide to scrap the sale of the Airbus stake, under the terms of an existing shareholder agreement it will not be able to sell again until next May.

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