The board of Marks & Spencer is bracing itself for fresh allegations this weekend about share-trading in the retail giant, which is the target of an GBP8.3 billion bid by the BHS entrepreneur Philip Green.

According to City sources, the allegations relate to when chief executive, Stuart Rose first knew about Green's takeover bid, and focus on a conversation at the Chelsea Flower Show on 24 May. Rose was appointed chief executive of M&S the weekend after the alleged conversation.