Blakeney Management, an investment fund seeking an overhaul of the Sub- Saharan group's board, claimed that the company had made defamatory remarks against some of its associates.
Blakeney, which owns around 9 per cent of Lonrho Africa, said its legal advisers had been instructed to take further action over comments made by the company in a circular to shareholders, analysts' presentations and a public statement on Thursday.
The remarks related to Miles Morland, Blakeney's chairman, John Jackson, chairman of leisure group Ladbroke, and Dekel Golan, chairman of African Plantations, an African company.
The three are Blakeney's candidates to replace Lonrho Africa's non-executive directors at a shareholders' meeting on December 10.
In the circular to shareholders, the company had questioned the three men's experience of working in Africa.
Blakeney, together with fellow fund African Lakes, where one of the Soros funds has a stake, wants to shake up the board and radically change the company's strategy.
The two funds want to break up the hotels-to-agriculture business, recently spun off from Tiny Rowland's mining group, by selling underperfoming parts.
A spokesman for Lonrho Africa dismissed Blakeney's threats as "absolute puffery".Reuse content