UPDATE 1-Board member at Brazil's Petrobras resigns amid legal confusion

(Adds information throughout on legal issues surrounding resignation)

RIO DE JANEIRO, April 16 (Reuters) - Petrobras board member Marcelo Gasparino has tendered his resignation, the state-run oil firm said on Friday, just four days after his election to the post, creating a potential eleventh-hour hurdle for its nearly complete management transition.

Gasparino, who represents market investors on the board, had previously said he planned to resign to force a new shareholders’ meeting. He said he would wait until after the board appointed a new chief executive, which occurred earlier in the day.

In a letter published on his LinkedIn account shortly before being elected to the Petrobras board at an extraordinary shareholders’ meeting on Monday, Gasparino criticized the allegedly confusing manner in which the meeting was held. He said it deprived market shareholders of their full voting rights.

He said his resignation would trigger a new shareholders’ meeting under Brazilian securities law, during which shareholders would have another chance to vote.

Petroleo Brasileiro SA, as the company is formally known, said in a Friday securities filing that a new board election is only required when members are forced out, not when they resign. It said the board could appoint a substitute until the next shareholders’ meeting, but did not specify a date.

In an excerpt of Gasparino’s resignation letter, which was included in the filing, he said his resignation would be effective May 31 or until his substitute is elected at a shareholders’ meeting.

The Petrobras board has seven government-appointed members, one representing workers and three representing market shareholders. A larger number of market-aligned members is generally seen as positive by the market, though some analysts question the importance of the board breakdown given that the government statutorily holds the majority of seats.

Reporting by Gram Slattery and Marta Nogueira; Editing by Richard Chang