The consortium of Amec, URS and Areva has had its contract renewed to manage the nuclear waste clean up programme at Sellafield despite fierce criticism over delays and costs.

The Nuclear Decommissioning Authority said it wanted to give the Nuclear Management Partners team further time to make “significant improvements” to the £1.8bn a year works programme.

NMP was awarded a 17-year contract in 2009, which included periodic break points at which it could be continued, cancelled or modified.

The first 5-year period comes to an end in March 2014.

A National Audit Office report last year into the running of the massive works programme concluded there had been up to £1bn of cost overruns on the project.

NDA CEO, John Clarke, said: “Sellafield is by far the most complex and challenging site in our portfolio, and we are determined to drive improved performance at the site.

“We have reviewed progress under the contract to date and concluded that the right decision is to extend the contract to give NMP further time to bring about the improvements in capability and performance at the site that we and they are looking for.”

He added: “While progress is being made on a number of fronts we will require significant improvements during the next 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 focussed on achieving our goal of safe, effective, value for money decommissioning at Sellafield – as we are seeing elsewhere across our portfolio of sites.”

Clive White, President of AMEC’s European Clean Energy business, said: “Sellafield is the one of the world’s most complex and challenging nuclear sites.

“NMP’s learning curve over the first five years has been a steep one, with many accomplishments as well as areas for improvement.

He added: “We will be focused on accelerating the clean-up of the high hazard legacy ponds and silos, which are acknowledged as the priority area.”