J Sainsbury confirmed this morning that it will open its books to Delta Two, the Qatari-backed fund proposing a 600p-a-share offer for the supermarket group.

The Times reported this morning that the announcement was expected today.

Delta Two hopes to make a formal offer in a few weeks, as part of which Tony Campbell, the former Asda executive, will replace Sir Philip Hampton as chairman. Sir Philip has held the job for three years.

Mr Campbell is a former colleague of Sainsbury's chief executive, Justin King. It is understood that Delta Two is keen to retain Mr King

Delta Two will meet Sainsbury's pension trustees this week to secure their backing for the £10.6 billion deal, which could entail the bidder stumping up a £2 billion up-front cash payment to underpin future retirement benefits.

The supermarket chain will allow Delta Two to conduct due diligence on the business for a "limited period" after the bidder revised its original proposal by adding £300 million in equity to the bid terms to reduce the debt element in the deal.

Shares in Sainsbury's rose 2.53 per cent this morning to 568p, below Delta Two's 600p offer price.

Sainsbury's stock price rose despite its being named in an Office of Fair Trading investigation accusing the group and four other British supermarkets of colluding with UK dairy producers to fix the prices of milk, butter and cheese in 2002 and 2003.

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