By Richard Valdmanis

DAKAR (Reuters) - Liberia's largest palm oil company, Golden Veroleum, needs to review its social and environmental policies after its workers damaged graves, cleared existing crops and polluted creeks, according to an independent study it commissioned.

The findings from The Forest Trust (TFT), a non-profit environmental consultancy, follow complaints from activists that the Singapore-controlled firm is violating commitments it made as a member of the Roundtable on Sustainable Palm Oil (RSPO), a global certification body for the industry.

Palm oil is the world's most important vegetable oil used in everything from margarine and soap to biofuel, with annual production around the world worth about $20 billion.

RSPO requires its members to adopt environmentally and socially responsible policies to improve the industry's record that has included forest destruction and pollution.

"There is materiality to a number of the claims made by the communities," according to the TFT report obtained by Reuters.

It said Golden Veroleum needed to review its land acquisition process, improve communication with locals, bolster its compensation process, and educate workers about the company's RSPO commitments, among other things.

"We acknowledge and accept the recommendations in the report and we expect to implement them," said Golden Veroleum spokesman David Rothschild. "If we have fallen short, we will try to improve."

Critics say the palm oil industry is taking part in a land grab in Africa that reduces local food output in favor of crops for export. Golden Veroleum's investment, however, was widely seen as a boon for Liberia, which is trying to rebuild after a 1989-2003 civil war that crippled its economy.

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TFT submitted the findings to Golden Veroleum in February but the document has yet to be released publicly. Global Veroleum commissioned TFT to do the study in January, saying it hoped the findings and recommendations would help it improve its operation in Liberia.

The report found at least four cases of workers apparently damaging ancestral cemeteries - including by planting trees on graves - and instances of farms being cleared without prior consent and creeks used for drinking water being polluted. The report added that compensation to victims was often inadequate.

"It is true that the number of seriously affected individuals has not yet been high, however our findings indicate that it could quickly increase as the operation progresses," according to the TFT report.

Golden Veroleum is owned by the U.S.-based Verdant Fund LP, whose sole investor is Singapore-listed palm oil giant Golden Agri-Resources, the world's second-largest palm oil plantation company.

It became Liberia's biggest palm oil investor in 2010 after announcing plans to spend $1.6 billion developing plantations over 220,000 hectares.

Golden Veroleum became an RSPO member in 2011, stating on its RSPO web page that: "All land development from the first acre, will be conducted in compliance with RSPO."

"Our investment ... will carefully preserve original and high conservation value forest and biodiverse areas, sacred and community lands," it continued.

RSPO membership is meant to help palm oil firms boost their access to markets and capital while improving community and labor relations and preventing environmental damage.

Golden Veroleum's Rothschild said the company was in discussions with RSPO over the incidents and that the company expected to retain its membership after implementing changes to its operations.

No Golden-Agri official could immediately be contacted in Singapore.

(Editing by Anthony Barker)