Fresh estimates show that it could cost double what was previously thought to build the Hinkley Point C nuclear power plant in Somerset.
An assessment published by the department for energy and climate change (DECC) yesterday shows that the figure has ballooned to £37bn from £14.5bn a year ago. It's due to new long-term forecasts for wholesale electricity prices, which determine the UK government's subsidy for Hinkley's output.
It comes amid speculation that post-Brexit vote uncertainty could lead EDF to abandon the much-delayed project. Concerns about its impact on the french utility giant's strained balance sheet have already created conflicts within firm.
Angus Brendan MacNeil, chair of the energy and climate select committee, previously told City A.M. "anything could happen" when asked if Britain's vote to leave the EU could result in the project being scrapped.
Read more: EDF to sell RTE stake to fund Hinkley Point
A spokesperson for the DECC said: "We have set the strike price to protect bill payers if energy costs go up or down, so the cost of the project to consumers will not change."
"The report from the infrastructure and projects authority does not suggest that the lifetime costs of Hinkley have increased. It is a snapshot of the position at the end of September 2015."