MPs have strongly criticised the private consortium that runs the Sellafield site in Cumbria.
The Public Accounts Committee says costs are out of control, and the contract with Nuclear Management Partners should not have been extended.
The Nuclear Decommissioning Authority which own the Sellafield site have said today that they will aim to achieve the recommendations laid out by the Public Account Committee but say they are already making progress.
“The NDA welcomes the scrutiny of the Public Accounts Committee (PAC) into our vitally important mission to decommission Sellafield.
"We have made good progress towards implementing the recommendations laid down by the PAC following its original report into Sellafield last year and will now focus on achieving the aims of the six recommendations set out in this latest report.
"Both NMP and the NDA now have a much better understanding of the issues and complexities that exist at the site and the challenges that lie ahead.
"Whilst progress has been made on a number of fronts we will require significant improvements during the next contract period. We have had extensive discussions with NMP and made clear where these improvements must be made.
"We will continue to monitor performance closely and remain focused on achieving our goal of safe, effective, value for money decommissioning at Sellafield – as we are seeing elsewhere across our portfolio of sites.”
Challenges of cleaning up waste at a Cumbria nuclear site are "unprecedented" and more complex than "any other operational or decommissioning nuclear site in the world", the head of the team overseeing Sellafield nuclear site.
NMP chairman Tom Zarges dodged claims costs were spiralling out of control and said the consortium was focused on building on "our experience of the last five years".
The challenges at Sellafield are unprecedented, with complexities exceeding any other operational or decommissioning nuclear site in the world, therefore demanding extraordinary technology and skills.
The first term of our contract has been characterised by many successes but also a number of disappointments and areas for improvement.
Our job now is to build on our experience of the last five years to safely and reliably deliver our customer's mission, while further accelerating the pace of change and providing value for money to the NDA, Government and the UK taxpayer.