In a move that could open up a can of worms in terms of corporate governance, Lord Browne told directors to go straight to junior managers at BP's grass roots to "make sure information is absolutely pure and not in any way distorted by trying to put things in favourable light."

Each manager then signed a personal report setting out what their unit could achieve and making them responsible for its contents. "It is important that they stand there and say, 'This is my opinion and no one else's," Lord Browne told the inquiry.

Lord Browne said the decision to go "right to the bottom of the organisation" to find out what went wrong had left some managers higher up "feeling very disenfranchised".

BP said in October it expected output to grow by 3% this year, compared to a 5.5% target in August. In addition, BP announced a 13% drop in profits for the three months from July to September, which in turn saw it stock price fall below £4 for the first time in four years.