The operational handover of HMS Audacious to the Royal Navy has been delayed by 17 months due to "technical issues" in production.
The 97-metre-long, 7,400-tonne nuclear-powered submarine is the fourth of seven vessels joining the Astute-class programme.
An MOD spokesperson said: "The Audacious operational handover delay has been caused by technical issues."
But they said it remains committed to delivering all seven Astute-class vessels by the end of 2026, and that HMS Audacious "is expected to commence sea trials by the end of this year."
BAE won the £1.2 billion contract to develop HMS Audacious in 2012.
Exactly what faults have caused the delay could not be disclosed by the Ministry of Defence, as doing so could jeopardise security and capability.
Similar delays could now be experienced in the delivery of HMS Anson, another Astute-class vessel, costing £1.3 billion.
Set-backs in the timings of the delivery to the Royal Navy have not caused the programme to overrun in costs, according to the MOD.