RIO DE JANEIRO, July 1 (Reuters) - Brazilian miner Vale has lost its second board member in less than four months, it said in a filing on Monday, reporting the resignation of Vera Marie Inkster.

Vale, which is in the process of looking for a new CEO, gave no reason for Inkster's resignation in the filing.

In March, Jose Luciano Duarte Penido also left the board of directors, saying in his resignation letter, seen by Reuters at the time, that the firm's succession process was being conducted in a "manipulated manner."

Days before Penido's exit, Vale had extended the term of Chief Executive Eduardo Bartolomeo until the end of the year, amid media reports that the Brazilian government was seeking to influence the choice of a new CEO.

Although Vale was privatized over 25 years ago, the government has continued to exert pressure on the miner's board of directors at times through public-sector pension funds.

Penido was favorable to fully renewing Bartolomeo's term, Reuters reported at the time, citing a source.

As Inkster and Penido were both independent board members, Monday's exit should trigger Vale to call for a shareholders meeting, as the number of independent members is now below the seven defined by the miner's bylaws.

In the filing on Monday, Vale said the board will call a meeting "in due course."

The company declined to provide further comment when requested by Reuters. (Reporting by Marta Nogueira; Writing by Andre Romani; Editing by Brendan O'Boyle and Sandra Maler)