The estimated cost of decommissioning the UK’s nuclear power plants had risen by almost a third to £73bn ($145bn) in the past five years, and could rise further, the National Audit Office warned on Tuesday.

In findings critical of the inconsistencies in official estimates, the NAO, the public spending watchdog, said the cost of decommissioning sites over their remaining lifetimes was currently £17bn more than the government’s estimate in 2003.