Mr Philip Green said yesterday that shareholders would have to decide whether to back his £9.1 billion (€13.6 billion) bid for Marks & Spencer within a day or two of being given a strategy update today by the company's new chief executive.

The group's board has already rejected Mr Green's 400p a share offer for the retailer, made through his bid vehicle Revival, on the grounds that it undervalues the chain.

Chief executive Mr Stuart Rose plans to outline why this is the case this morning as he gives a trading update and outlines his strategy for the group.

But Mr Green told BBC1 Television's Breakfast With Frost programme that shareholders would have to make their minds up within hours of the update.

He said: "As far as I'm concerned, within 24 or 48 hours of Monday morning, it will be make-your-mind-up time in terms of the shareholders.

"We will then make a decision very, very soon thereafter, and the shareholders will have to decide do they want to be with me and take the money today, or do they want to stay where they are."

He has previously vowed only to make a formal bid with the support of the board, but the UK's Takeover Panel has imposed a deadline of noon on August 6th for a firm offer to be tabled.

Mr Green said the company was in need of "major surgery", and said that for a long time it had not had anyone with the "feel, touch, passion, flare and enthusiasm" to develop it.

He also hinted that he would be prepared to sell Bhs if the competition authorities required him to in order to press ahead with the M&S bid. He said: "We will do what we have to do if that's required."

The interview came just hours after it emerged that Mr Green may have to pay millions of pounds a year into M&S's pension scheme if he is successful with his bid.

The scheme currently has a £670 million deficit under the snapshot accounting standard FRS17.

But the trustees have warned that in the most extreme case, Mr Green could be forced to pay up to £785 million a year into the scheme for three years.

Meanwhile the group's new chief executive Mr Rose is expected to promise to return between £1.65 billion and £2.3 billion to shareholders when he gives his strategy update.