M&G, the biggest shareholder in Lonmin with 17 per cent of the shares, has rebuffed Xstrata’s hostile offer, which values the London-based platinum producer at £5bn.

The investment group, which has accumulated its stake in Lonmin over several years, deemed Xstrata’s £33-a-share cash offer too low for what it believes are unique platinum assets. M&G’s decision comes two days after Xstrata approached leading investors in Lonmin in the hope of buying 24.9 per cent of the group.