Marks & Spencer's pension trustees have dropped a bombshell into the battle for control of the company by warning Philip Green may have to inject hundreds of millions of pounds into the pension fund if his bid for M&S Succeeds.

In a statement published on Saturday, the trustees set out five options for filling the fund's GBP185m current deficit if M&S were acquired by a highly leveraged buyer.

The most extreme demand - for an investment solely in safe but low-return bonds - would cost Green an extra GBP785m a year over three years. Analysts said the trustees' statement could be the beginning of a "poison pill" that could torpedo Green's GBP9.1 billion takeover proposal for the company. If Green walks, M&S's share price could plunge.