text: Fitch cited higher estimates for the size of the oil spill and US calls for the group to place funds in an escrow account to fund any potential liability claims.
  BP's shares fell 0.5pc to 353p in afternoon trading in London after what was the first multi-notch downgrade of BP by any of the three major rating agencies and the first that left it below double A.
  The 'BBB' rating is just two notches above junk status.
  "The principal changes in circumstances ... include the indication late last week from US government scientists of a significantly higher spill rate than previously announced by all parties, which Fitch expects will materially increase BP's exposure to Justice Department fines," Fitch said.
  It also added that there was a "significant step-up in action from the US government surrounding calls for pre-emptive escrowing of damage claims".
  "Both of these events have a direct bearing on BP's fundamental financial flexibility."
  BP credit-default swaps surged 39 basis points after the downgrade to 476.5, according to CMA DataVision.
  The oil spill has already cost BP some $1.6bn since the Deepwater Horizon rig it leased sank on April 22, and it may have to pay out several more billions.
  Senator Harry Reid on Monday requested that BP set aside a $20bn independent fund to speed up the claims process for victims of the spill.
  Fitch sliced the rating from AA+ by a notch on June 3, matched with similar moves earlier this month by Moody's and Standard and Poor's who currently have the company on the Aa2 and AA- respectively.