The group added: 'Marketing margins have decreased sharply in the first quarter relative to the previous quarter, and were also below those of a year ago.'
First-quarter output across BP's vast collection of producing fields is likely to come in at around 4.09m barrels a day, broadly in line with the end of last year.
Analysts, who have been upping their forecasts for BP on the back of the surging oil price, were expecting slightly stronger growth.
Browne, who bagged £5.65m in pay and bonuses last year, is set to return up to $23bn to investors through dividends and buybacks this year. BP handed back $7.5bn in 2004.