Yesterday a White House spokesman promised to keep a “boot on the throat” of BP and today the shares are down nearly 5%.

BP shares dropped as much 30 pence, to 546 pence today, the lowest in seven months. Overall the shares have fallen around 14 percent since the Deepwater Horizon well exploded and sank on April 20.

Bloomberg: So far the spill has had little impact on refining, shipping and production in the Gulf, said Tom Bentz, a broker at BNP Paribas Commodity Futures Inc. in New York. Traders are “trading on fear” in case the situation changes, he said yesterday. “Everyone is watching it. People are afraid that shipping could be cut off.”

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BP has said the cost of containing the spill and securing the original well is running at about $6m (£3.9m) a day. But the true cleanup bill could cost billions.

Drilling firm Transocean that owned and operated the equipment has seen its shares fall nearly 20% since the explosion.