Ministers have failed to properly understand the risks entailed in their decision to leave Britain without an aircraft carrier for almost a decade, the Whitehall spending watchdog has warned.
The National Audit Office said changes to the carrier programme in the Government's Strategic Defence and Security Review (SDSR) had created "significant levels of operational, technical, cost and schedule uncertainty".
In a highly critical report, the NAO warned there were "major risks" surrounding its plans to reconstitute a carrier strike force from 2020 onwards.
It said the Ministry of Defence will not have "matured its understanding" of the consequences of its decisions for another two years, with the final cost of the programme now set to exceed £10 billion.
The NAO also disclosed that military chiefs had recommended axing the carrier programme altogether in favour of keeping more surface ships, such as frigates and destroyers.
However, they were overruled by the MoD on the grounds that it would have been "unaffordable" in the short-term due to the cancellation costs, even though it would have led to "significant" medium-term savings.
The release of the report provoked a furious row in Whitehall, with the MoD complaining that it had been published before they had agreed the final text, in contravention of normal practice.
The NAO, in turn, said that it had been denied access to crucial Cabinet Office papers which they needed to see in order to understand the decision-making process behind the SDSR.
Margaret Hodge, the chairman of the Commons Public Accounts Committee which oversees the work of the NAO, said the "lack of transparency" over such a costly and important programme was "not acceptable".
However, Defence Secretary Liam Fox insisted that the decisions in the SDSR had put the carrier programme "back on track" while cutting the overall costs by £3.4 billion.