Oil giant BP said William Castell, the head of its safety committee, will leave its board in April as the reshaping at the top level of the company continues in the wake of the Gulf of Mexico oil spill.

BP said on Friday that William Castell, chair of its safety, ethics and environment assurance committee since 2008, will not seek re-election at the company's annual meeting in April.

Andrew Shilston will succeed Castell in the role of senior independent director, the company added, while Ann Dowling, head of the department of Engineering at the University of Cambridge, will join the board and safety committee.

The changes follow significant adjustments to the company's board over the last two years, many of which came after BP's doomed Macondo well gushed four million barrels of oil into the Gulf of Mexico after an explosion in April 2010.

Castell was head of the committee at the time of the spill, when BP's safety standards were vigorously questioned. He passed leadership of the committee to fellow board member Paul Anderson in December 2011, BP said.

Investors expressed their displeasure at Castell last year when 25 percent of investors who voted ahead of BP's annual meeting, representing 60 percent of shares, voted against his re-election.

(Reporting by Sarah Young and Tom Bergin, Editing by Rosalba O'Brien)