DEEP-WaTER drilling could take place at hundreds of sites off the British coast after MPs ruled out a moratorium, despite concerns that the work could lead to a disaster worse than BP's oil spill in the Gulf of Mexico.  Following the Deepwater Horizon accident last year, the energy and climate change committee was asked to look into the risks of drilling in deep water off Britain. Oil companies have admitted that plans for deep-water drilling off the Shetland islands could cause an oil spill worse than the Gulf of Mexico disaster.  But Tim Yeo, the chairman of the committee, said the energy supplies and national security of Britain depends on the newly discovered oilfields.  He said safety procedures could be "tightened up" but on the whole the industry is safe and the regulatory system "robust" following the reforms brought in after the Piper alpha oil rig disaster in 1988.  "although we heard evidence it is not always done right - and I am sure it is not always done right - nevertheless, I think the concerns are nothing like big enough to justify stopping the process," he said.  a quarter of Britain's discovered oil and gas reserves, about four million barrels, lie in deep water off the west of Shetland.  Oil companies are drilling in the