Credit ratings agency Standard & Poor's downgraded French utility giant EDF despite the UK government giving the green light to the £18bn Hinkley Point C nuclear power plant.
It said construction risks linked to the project are high and that the large investments associated with it will weigh on EDF's already pinched cash flow.
There have long been concerns over whether EDF's already stretched balance sheet will be able to cope with the huge project. Moody's said last week it had placed EDF's rating on review for a downgrade.
S&P chopped its rating to 'A-/A-2' from 'A/A-1' citing higher execution and contingency risks for the project. This will hamper its large additional investments at a time when the firm is already bleeding cash.
The utility giant also faces high risks relating to the construction of a similar nuclear reactor in Flamanville which is due to start generating in 2018, it added.
But the credit ratings agency kept its outlook stable due to the state-backed firm's plans to reduce its net debt over the next three years. It's announced plans for a €4bn (£3.44bn) capital increase, €10bn worth of disposals and €1bn cost cuts.
Whitehall recently approved plans to build Hinkley but with revised conditions to allay security concerns, paving the way for other nuclear power plants to be built in the future.
The measures would ensure EDF remains the controlling partner during the construction phase.