A whistleblower identified by The Daily Telegraph newspaper in London as a "BP employee" alleges in a letter sent to the newspaper that a "serious case of bribery and corruption" has occurred within the company's tanker chartering division.
The letter states that tankers were chartered under preferential terms in exchange for cash payments to a senior BP employee.
"With the above information we expect you to take all necessary action to protect the shareholders' interests and safeguard BP's reputation for anti-corruption and bribery," a copy of the letter, also sent to BP Chief Executive Officer Bob Dudley, reads.
A spokesman for the energy company told the newspaper it received a copy of the letter a week ago and was investigating the claims.
"BP conducts its business to the highest ethical standards," the spokesman said. "We take all allegations of this sort extremely seriously and always investigate them."