BP (BP.L) on Tuesday reported its worst annual loss in at least 20 years and thousands more job cuts as the British oil and gas company grappled with a collapse in oil prices. The energy company reported an annual loss of $6.5 billion for 2015, even worse than its 2010 results when it counted the costs of the deadly Gulf of Mexico oil spill. BP said it would cut 3,000 jobs in its downstream unit by the end of 2017 on top of 4,000 cuts already announced in oil and gas production as part of a $2.5 billion restructuring program announced last year.