The massive earthworks needed to prepare the ground for a new nuclear power station at Hinkley in Somerset have been delayed, the Guardian has learned, dealing a significant blow to the government\'s energy plans. Half of the big six energy companies have already abandoned their nuclear plans as too expensive, but the Hinkley plant is backed by the most pro-nuclear energy company, EDF, which is 83% controlled by the French state. Replacing the UK\'s ageing nuclear plants is central to the government\'s current plans to cut greenhouse gas emissions while keeping the lights on. EDF was seen as the most committed company, with France getting three-quarters of its electricity from nuclear power. But reports of rising reactor costs and the election of Francois Hollande as French president, promising to cut back nuclear power, has dented confidence. UK energy company bosses have stressed the need for ministers to ensure their energy market reform plans, set out in the Queen\'s speech, to make new nuclear power stations an attractive investment. The earthwork preparation of the Hinkley site, involving moving millions of cubic metres of soil and rock, was due to begin in August, according to West Somerset Council\'s planning department. But EDF staff have been told the work will now start in 2013, according to information obtained by the Guardian. Crispin Aubrey, of the Stop Hinkley campaign, said: \"This is very good news. We have always argued that it\'s appalling vandalism to destroy over 400 acres of Somerset countryside before they even have permission to construct the proposed reactors. This is yet another sign that the UK\'s dangerous nuclear enterprise is stumbling.\" EDF is expected to get the government\'s go-ahead to build the reactors within the next year, and will make its final investment decision by the end of 2012. \"We aim to start the earthworks as soon as practicable and all necessary steps are being taken to ensure that work can start in good time,\" said an EDF spokesman. He added some preparatory work had begun since planning permission was granted in February, including cutting hedgerows, demolishing old buildings and closing footpaths. Internally, EDF blamed the delay on cost overruns on the preparatory work. One source involved in the project told the Guardian the work so far had been a \"farce\". The £100m earthworks contracts were awarded to construction companies Keir and BAM Nuttall in February, days after David Cameron and Nicolas Sarkozy agreed a wide-ranging nuclear power deal. Both companies declined to comment on the earthworks delay. The delay comes at a highly sensitive time as EDF and other companies negotiate with the government over the financial support that will be available to nuclear and other low-carbon energy sources, such as wind and solar power. On Friday, the chief executive of Centrica, which has a 20% stake in EDF\'s nuclear plans, issued a warning to ministers. \"The investment case for nuclear has yet to be proven,\" Sam Laidlaw told investors. Earlier, EDF\'s chief executive, Vincent de Rivaz, said: \"It is absolutely critical that the government continues to make steady, tangible progress with its electricity market reform plans.\" EDF has been criticised as being too close to government, providing full-time staff to work within the Department of Energy and Climate Change. Energy minister Charles Hendry will be questioned by MPs on the nuclear challenge on Tuesday. A DECC spokeswoman said: \"It is for energy companies to construct, operate and decommission nuclear power stations. EDF\'s application for development consent for the nuclear power station itself envisages operations starting in 2019.\" \"The flagship nuclear project in Britain is now surrounded with confusion and is going nowhere fast,\" said Doug Parr, Greenpeace chief scientist: \"It\'s time for the government to admit that the economics of nuclear power just don\'t stack up. Only blank cheques from the taxpayer will keep the show on the road.\" The cost of the two nuclear plants EDF intends to build in Somerset was reported last week to have risen by 40% to £7bn each. Peter Atherton, an influential energy analyst at Citigroup, said in a report: \"If construction costs are indeed anything like that, then an already very challenging programme may be reaching the point of impossibility.\" An EDF spokesman said: \"Information about costs will be made public in due course, taking account of all the relevant factors. We remain committed to delivering the first new nuclear plants in the UK for 20 years at Hinkley Point. The decision depends on having the correct market framework that will allow an appropriate return on the massive investment required.\"