M&S shareholders are being urged to vote against appointing Sir Stuart Rose as executive chairman as this would spell ‘a dangerous concentration of power’.

Pension Investment Research Consultants Ltd, which advises institutional investors, said making Sir Stuart chairman while he was still chief executive breached corporate governance best practice.

‘Combining the roles represents a dangerous concentration of power that is potentially detrimental to board balance, effective debate and board appraisal,’ PIRC wrote in guidance to members.

‘We do not consider the circumstances, nor the company's rationale, to be sufficient to warrant the move,’ it added.

The organisation said that, along with a number of clients, it had explored the possibility of filing a shareholder resolution to address the specific question of concentration of powers, providing an alternative outlet for investor concern.

However, M&S claimed that PIRC had missed a deadline unless it was able to foot the bill for circulating the resolution separately before its AGM on the 9th July.

An M&S spokesman said: ‘We feel we have set out our arguments very clearly in the past and detailed the checks and balances we would put in place with our shareholders.’

M&S sent out a letter to all shareholders on 3rd April outlining two new board appointments, the strengthening of Ian Dyson’s role to group finance and operations director and a revised executive committee membership.