Interbrew has launched criminal proceedings for the theft and falsification of documents, after leaked papers suggested the Stella Artois maker was set to bid for South African Breweries.
The Belgian group said yesterday it had filed the claim, against "persons unknown" with the Brussels Court of Justice to protect its rights while it sought to identify the source of the leak.
An Interbrew spokesman said: "We have introduced a complaint but at the moment we do not know who is behind this criminal offence. We want to preserve our rights."
As well as theft and falsification, the claim alleges market manipulation, and includes a civil claim for damages.
Last Wednesday, shares in SAB surged eight per cent and Interbrew stock dropped four per cent after reports suggested Interbrew could launch a £4bn takeover bid this month.
Hugo Powell, chief executive of Interbrew, later confirmed his company had examined a possible merger with SAB, but said no timetable had been set.
While parts of the leaked document appeared authentic, significant aspects, including the actual alleged, had been falsified.
Meanwhile, Interbrew's announcement on Monday that it had no immediate plan to bid for SAB means the matter is no longer within an "offer period". The Takeover Panel has therefore passed the matter to the Financial Services Authority to examine.
But the Belgian brewer did not rule out a bid within the next six months, after a relaxing of takeover panel rules. Normally a potential buyer would be forbidden from returning to the table within six months of a denial.
It was deemed that since Interbrew had not submitted a formal approach the rule would not apply.