The cost of cleaning up the mess left by Sellafield nuclear power station in Cumbria was revealed yesterday to have soared by £5 billion last year to a staggering £53bn.

Nuclear power generation union GMB said the system used by decommissioning firm Nuclear Management Partners (NMP) did not work.

“GMB has been absolutely clear all along that the NMP model did not and will not work at Sellafield,” said GMB regional officer Chris Jukes.

He accused NMP of poor management causing “unbelievable decisions on expenditure.”

Commons public accounts committee chairwoman Margaret Hodge revealed the cost increase.

Mr Jukes said the committee had “undertaken some important work of scrutiny and we expect answers from NMP to some basic questions for our members in Sellafield, their families and communities.”

He added that GMB would raise the questions in a hearing with the Commons committee on March 11.