Tony Hayward, who will step down as BP boss in October after a career at the oil giant spanning almost 30 years, said it was right for the company to pursue a change of leadership following the Gulf of Mexico disaster.
In a statement issued by BP alongside today's second-quarter results, Mr Hayward said: "The Gulf of Mexico explosion was a terrible tragedy for which - as the man in charge of BP when it happened - I will always feel a deep responsibility, regardless of where blame is ultimately found to lie.
"From day one I decided that I would personally lead BP's efforts to stem the leak and contain the damage, a logistical operation unprecedented in scale and cost.
"We have now capped the oil flow and we are doing everything within our power to clean up the spill and to make restitution to everyone with legitimate claims.
"I would like to thank all of the BP people involved in the response and the many thousands of others along the Gulf Coast who have joined us in our efforts.
"I believe the decision I have reached with the board to step down is consistent with the responsibility BP has shown throughout these terrible events. BP will be a changed company as a result of Macondo (the well which exploded) and it is right that it should embark on its next phase under new leadership.
"I will be working closely with Bob Dudley over the coming months to ensure a smooth transition.
"It has been a privilege to serve BP for nearly 30 years and to lead it for the last three.
"I am sad to leave so many fine colleagues and friends who have helped this great company to achieve so much over the years.
"I am sorry that achievement has been overshadowed by the tragedy in the Gulf of Mexico."