Leading article: Black marks all round

The disgraceful episode that was the BP oil disaster in the Gulf of Mexico has become even more so with the news that officials from both Halliburton and BP had been told beforehand that the cement to be used to seal the bottom of the well – and thus prevent such an explosion from occurring – was unstable.

But they went ahead anyway. On 20 April, the Macondo well blew up, killing 11 rig workers and creating the biggest oil spill in US history, inflicting billions of dollars' worth of economic and environmental damage. It is now clearer than ever that cutting of corners by companies in pursuit of profit, and grossly inadequate supervision by government regulators, were mainly to blame. Naturally, Halliburton, which manufactured the cement, is disputing the new findings released by the presidential commission set up to investigate the disaster. It says that early tests on the cement mixture suggesting that there were problems were "preliminary", and that, in any case, it had informed BP. But the findings contradict statements from Halliburton officials at earlier probes of the Deepwater Horizon disaster that the cement was perfectly stable – and that the main fault lay with BP for using too few centralisers – elements that ensure the drilling pipe is properly centred in the well.

BP, equally naturally, blames Halliburton, and the argument will continue. Suffice it to note that Halliburton, which was led between 1995 and 2000 by the former US vice-president Dick Cheney, has been involved in several controversies, including the alleged overcharging of the US military for work in Iraq and bribes paid by its former subsidiary KBR to top officials in Nigeria. If it is deemed to be significantly liable for the disaster in the Gulf of Mexico, the financial consequences could be extremely serious – as evinced by the 16 per cent plunge in the company's share price when word first came of the commission's report.

But responsibility also lies with the US government. It is all very well to conduct rigorous inquires after the event. The truth is that the agency of the Interior Department supposedly policing oil well safety in the Gulf was so understaffed that the companies in effect wrote their own rules. This was a tragedy that should never have happened.