Royal Dutch Shell has admitted to setting overly aggressive targets and miscalculating the challenges of developing its flagship Sakhalin 2 oil and gas project in Russia, which has doubled in cost to $20bn (£11.6bn) and is running about eight months behind schedule.

In an interview, Linda Cook, the group's head of gas and power, said: "We set a very aggressive target in terms of cost and schedule and as it's proven out over the two or three years since we made the decision to move forward, it was much more aggressive than it should have been given the realities of the project that we now understand."