(Recasts story, adds Fininvest's complaint, details)
By Mathieu Rosemain and Gwénaëlle Barzic
PARIS, Dec 19 (Reuters) - Vivendi Chairman Vincent Bollore added pressure on Italian tycoon Silvio Berlusconi on Monday as the French media giant said it would beef up its stake in Mediaset up to the threshold triggering an all-share bid.
The move comes about a week after Vivendi bought a fifth of Mediaset, the Italian broadcaster controlled by Berlusconi, in a move that stoked an ongoing row between the companies over a pay-TV deal.
"Vivendi's management board met today and decided... to increase its investment in Mediaset by acquiring additional shares depending on market conditions within the limits of 30 percent of the share capital and voting rights," the company said in a statement.
Berlusconi's family holding Fininvest, which holds 38.3 percent of Mediaset, said earlier on Monday that it had filed a market abuse complaint against France's Vivendi with national market authority Consob.
Fininvest also asked Consob to exercise all the powers it has under an Italian financial regulation, which includes among other possibilities the seizure of company assets.
Mediaset declined to comment on Vivendi's statement. Vivendi declined to comment on Mediaset's complaint to Consob.
Vivendi denied on Saturday it was planning to take over Mediaset after buying 20 percent of the Italian broadcaster's capital in a move that has riled the government and stoked an ongoing row between the companies over a pay-TV deal. (Reporting by Mathieu Rosemain and Gwenaelle Barzic; editing by John Irish)