BP sinks as US government sues over Deepwater spill

After months of negative headlines following the Gulf of Mexico oil spill, BP seemed to have turned something of a corner lately. But the US government isn't done yet: as expected, it has just launched its legal action against BP and the other companies involved in the Deepwater Horizon blow-out - using fairly belligerent language, too. BP has already set aside a hefty $40bn pot to cover its costs, which should be enough (unless the government can prove gross negligence, perhaps). But with a lengthy and costly negotiation process now unavoidable, perhaps it's no wonder BP's share price has taken a hammering this morning...

The US government is suing BP and eight other firms for 'violations of safety and operational regulations' under the US Clean Water Act and Oil Pollution Act; it wants them to have unlimited liability for all the clean-up and compensation costs, the full extent of which are still to be established. BP has already been sued more than 300 times by people or groups in the area, but this is obviously the biggie: some analysts argue that if the government succeeds in proving gross negligence, the final cost could be as much as twice BP's $40bn estimate.

However, this is very much a worst case scenario. Proving gross negligence is likely to be a tough ask; many think a more likely outcome is that the various parties will start haggling over a settlement to prevent this ever getting to court. For both BP and the government, a public trial is likely to be embarrassing, expensive and very time-consuming. So a negotiated settlement seems like the most sensible option all round.

BP has been quick to point out that these are still just allegations. But it struck a conciliatory tone in the statement it produced in response today, promising to answer the charges 'in a timely manner' and to co-operate with all the ongoing investigations. One thing's for sure: it clearly won't be able to rely on a 'collective responsibility' line from the other firms involved: most of them have been quick to remind everyone that it's all BP's fault and nothing to do with them, honest guv.

The trouble is that with the best will in the world, these negotiations are going to take time - and throughout that time, BP will continue to have a cloud hanging over it. Hence why investors have been a bit spooked - BP's share price fell about 3% this morning, which is a lot for a company of BP's size (equivalent to nearly £3bn of value). Today's lawsuit is a reminder that this nightmare is still far from over for BP, whatever the progress it's been making under new boss Bob Dudley.