Up to a fifth of Marks & Spencer’s shareholders are expected to vote against chief executive Sir Stuart Rose’s promotion to chairman.

20 per cent of shareholders will express their disapproval at M&S's AGM on July 9, according to reports.

In addition, there could be a substantial vote against proposals to change M&S's boardroom incentive plans that will allow directors to achieve big payouts more easily, according to the Guardian.

Rose’s promotion to M&S executive chairman goes against City best practice, which favours independent, external non-executive candidates for the role of chairmen and states that chief executives should not be appointed to the role.

Rose wants to do both jobs for three years and said he will put himself up for re-election annually, in an effort to appease unhappy investors.

Separately, Rose said last week that food inflation was nearer 10 per cent than 2 per cent, in direct contrast to the assessment of Sainsbury’s chief executive Justin King, who said last month that food inflation was at 2 per cent.