By Guillermo Parra-Bernal

SAO PAULO (Reuters) - Shareholders of Brazilian telecom carrier GVT on Tuesday unanimously removed a poison pill clause that was an obstacle to a merger by making takeover bids too costly.

The Curitiba, Brazil-based company is the target of an unsolicited $3.7 billion bid by the domestic unit of Spain's Telefonica and a friendly $3 billion approach by France's Vivendi. Both suitors had made the removal of the poison pill a precondition for their bids.

The decision scrapped two articles from the company's statutes forcing bidders to present shareholders of GVT with a cash offer equal to 125 percent of the highest value of the company's stock price over the prior 12 months.

"This effectively removes the anti-takeover mechanism for all qualified bidders," Morgan Stanley analyst Vera Rossi wrote in a note to clients after the decision.

GVT shareholders approved a new minimum of at least 48 reais a share for any bid. The buyer must now pay for GVT in cash before Feb. 28, 2010.

So far, the only firm bid available to GVT shareholders was from Telefonica's Telesp unit. Yet, GVT's board of directors confirmed both Telefonica and Vivendi as qualified bidders for the company.

Telesp's 48-reais-a-share bid is 14 percent higher than Vivendi's 42 reais-per-share offer reported on Sept. 9 -- which still has to be made official.

To muscle out Telefonica, Vivendi would have to offer a minimum 50.4 reais a share, according to Itau Securities analyst Walder Nogueira.

Telefonica has said it expects regulatory approval from the Brazilian telecommunications industry watchdog Anatel before an offer, initially set for Nov. 19.

Shares of GVT jumped 1.3 percent on Tuesday to 51.03 reais in Sao Paulo. The stock has almost doubled this year.

(Additional reporting by Cesar Bianconi in Sao Paulo; Editing by Dave Zimmerman, Phil Berlowitz)