Pressure is also being exerted on Charles Saatchi to try to force him to state whether he remains loyal, and intends to fully honour his employment contract with Saatchi & Saatchi, where he is honourary life president.
The action over the brothers' investment in Adidas, the German sports company headed by Robert Louis-Dreyfus, former chief executive of Saatchi & Saatchi, had been on the cards since the acrimonious in-fighting on the board became public in December when Maurice Saatchi was ousted as chairman.
A stiff six-point response was made by the brothers to this latest of several writs issued recently by the company.
Among the main points, they said: "The investment in Adidas was brought to Maurice and Charles Saatchi by Robert Louis-Dreyfus when he was chief executive of Saatchi & Saatchi as a personal investment by the three of them.
"They notified the investment to the board of Saatchi & Saatchi at the time on 16 February 1993 and this was minuted by the board on 8 March 1993."
Directors of Saatchi & Saatchi were left in the lurch when Charles failed to turn up to face questions about his role with the company in the light of his recent statement that "in time" he wanted to join his brother's new agency.
"We are now considering what to do about [Charles's] position. We have not yet had any clarification from him about what he is doing," the company said. Charles has told friends that the only way he would leave Saatchi & Saatchi would be if he was fired.