BP's plan for a controversial deep-water oil well off Shetland should be halted by the Government, four of Britain's biggest green groups said last night.  The Royal Society for the Protection of Birds (RSPB), Greenpeace, the World Wide Fund for Nature (WWF) and Friends of the Earth urged the Energy Secretary, Chris Huhne, to refuse consent for the oil giant's proposed North Uist well as any spill from it would pose a "significant risk to wildlife" in one of the UK's most environmentally sensitive areas.  In a joint letter to Mr Huhne, the groups' leaders expressed anger that none of them had been made aware of BP's "public consultation exercise" about the well - which ended last week without a single response from the public - and raised concerns about the difficulty of coping with a deep-water oil leak in the hostile conditions of the North atlantic.  The Independent disclosed yesterday that BP's own