Decommissioning Sellafield will now cost £67.5 billion and the cost is continuing to rise, according to a new report.
The chair of the Public Accounts Committee Margaret Hodge said a solution to the problem of long-term storage of nuclear waste was as far away as ever following last week's decision by leaders of Cumbria County Council not to press ahead with a study for a possible long-term underground storage site.
The committee said the "enormous" legacy of nuclear waste at the Sellafield site has been allowed to build up and it was not clear what wider economic benefits had been achieved from the amount of public money spent at Sellafield - currently around £1.6 billion a year.
It added that the Nuclear Decommissioning Authority (NDA), the authority dealing with the country's nuclear legacy, had not been able to show what value it was getting for the taxpayer.
Ms Hodge, who laid the blame on successive governments’ inaction, said: "An enormous legacy of nuclear waste has been allowed to build up on the Sellafield site.
"The NDA believes that its decommissioning plan is credible but it has not been sufficiently tested and uncertainties remain - not least around what precisely is in the waste that lies in the legacy ponds and silos.
“It is unclear how long it will take to deal with hazardous radioactive waste at Sellafield or how much it will cost the taxpayer. Of the 14 current major projects, 12 were behind schedule in the last year and five of those were over budget."
Ms Hodge said taxpayers were not getting a good deal from the NDA's arrangement with international consortium Nuclear Management Partners on a plan to improve Sellafield Ltd's management of the site.
John Clarke, chief executive officer of the NDA, said: "Prior to the NDA's inception there was no credible lifetime plan for Sellafield and tough decisions about how we ultimately decommission the site had simply been put off for future generations to deal with.
“We are now facing up to those challenges and for the first time we have a proper plan in place for the decommissioning of Sellafield which lays out in detail programmes of work for every area of the site. Since the creation of the NDA in 2005, the financial investment at Sellafield has increased from £900 million to over £1.5 billion a year.
“There are a significant number of existing facilities on site already storing high and intermediate level waste that meet the highest international standards and the Sellafield plan includes an ongoing construction programme of surface stores over the next ten to fifteen years, to be built to these standards, valued around £600 million.
“This makes Sellafield one of the largest construction sites in Europe. Of course, not everything has gone smoothly on such a complex and highly-technical programme, and the report has rightly pointed to areas where we and the site need to do better."